View source for Early expansions of hominins out of Africa

{{Short description|First hominin expansion into Eurasia (2.1–0.1 Ma)}}
{{About|spreading theory of early humans before about 200,000 years ago|migrations of anatomically modern humans|Recent African origin of modern humans}}
[[File:Spreading homo sapiens la.svg|thumb|upright=1.8|Successive dispersals of {{color box|#e8e22c}} ''[[Homo erectus]]'' (yellow), {{color box|#e4ca30}} ''[[Neanderthal|Homo neanderthalensis]]'' (ochre) and {{color box|#e9252c}} ''[[Human|Homo sapiens]]'' (red, ''[[Out of Africa II]]''), with the numbers of years since they appeared ''[[before present]]''.]]
Several expansions of populations of [[archaic humans]] (genus ''[[Homo]]'') out of Africa and throughout Eurasia took place in the course of the [[Lower Paleolithic]], and into the beginning [[Middle Paleolithic]], between about 2.1 million and 0.2 million years ago (Ma).
These expansions are collectively known as '''Out of Africa I''', in contrast to the expansion of ''[[Human|Homo sapiens]]''
([[early modern human|anatomically modern humans]]) into Eurasia, which may have begun shortly after 0.2 million years ago (known in this context as "[[Recent African origin of modern humans|Out of Africa II]]").<ref>The term "Out of Africa I" is informal and somewhat rare.
The phrase ''Out of Africa'' used on its own generally refers to "Out of Africa&nbsp;II", the expansion of anatomically modern humans into Eurasia.
"Out of Africa I" is used in 2004, in Marco Langbroek, '' 'Out of Africa': an investigation into the earliest occupation of the Old World'', p. 61,
and as the title of a collection of essays, J. G. Fleagle et al. (eds.), ''Out of Africa I: The First Hominin Colonization of Eurasia'' (2010).
see also: {{cite journal |author=Herschkovitz, Israel|display-authors=etal|title=The earliest modern humans outside Africa |date=26 January 2018 |journal=[[Science (journal)|Science]] |volume=359 |issue=6374 |pages=456–459 |doi=10.1126/science.aap8369 |pmid=29371468 |doi-access=free |bibcode=2018Sci...359..456H |hdl=10072/372670 |hdl-access=free }};
{{cite journal |first1=Stella |last1=Hurtley |first2=Phil |last2=Szuromi |year=2005 |title=Out of Africa Revisited |volume=308 |issue=5724 |page=922 |doi=10.1126/science.308.5724.921g |journal=Science|s2cid=220100436 }}</ref>
The earliest presence of ''Homo'' (or indeed any [[hominini|hominin]]) outside of Africa dates to close to 2 million years ago.
A 2018 study claims hominin presence at [[Shangchen]], central China, as early as 2.12 Ma based on
[[Magnetostratigraphy|magnetostratigraphic dating]] of the lowest layer containing stone artefacts.<ref name=Zhu2018>{{Cite journal|author1=Zhu Zhaoyu (朱照宇)|last2=Dennell|first2=Robin|author3=Huang Weiwen (黄慰文)|author4=Wu Yi (吴翼)|author5=Qiu Shifan (邱世藩)|author6=Yang Shixia (杨石霞)|author7=Rao Zhiguo (饶志国)|author8=Hou Yamei (侯亚梅)|author9=Xie Jiubing (谢久兵)|author10=Han Jiangwei (韩江伟)|author11=Ouyang Tingping (欧阳婷萍) |year=2018|title=Hominin occupation of the Chinese Loess Plateau since about 2.1 million years ago|journal=[[Nature (journal)|Nature]]|volume=559|issue=7715|pages=608–612|doi=10.1038/s41586-018-0299-4|pmid=29995848|issn=0028-0836|bibcode=2018Natur.559..608Z|s2cid=49670311}}
"Eight major magnetozones are recorded in the Shangchen section, four of which have normal polarity (N1 to N4) and four of
which have reversed polarity (R1 to R4). By comparison with the geomagnetic polarity timescale [...] magnetozone N4 corresponds to the Réunion excursion (2.13–2.15&nbsp;Ma) in L28."</ref>
The oldest known human skeletal remains outside of Africa are from [[Dmanisi]], [[Georgia (country)|Georgia]] ([[Dmanisi skull 4]]), and are dated to 1.8 Ma. These remains are classified as ''[[Homo erectus georgicus]]''.
Later waves of expansion are proposed around 1.4 Ma (early [[Acheulean]] industries), associated with ''[[Homo antecessor]]'' and 0.8 Ma ([[Cleaver (tool)|cleaver-producing]] Acheulean groups), associated with ''[[Homo heidelbergensis]]''.<ref name="Bar-Yosef, O. 2001">{{cite journal |author-link=Ofer Bar-Yosef|last1=Bar-Yosef |first1=O. |last2=Belfer-Cohen |first2=A. |year=2001 |title=From Africa to Eurasia – early dispersals |journal=[[Quaternary International]] |volume=75 |issue=1 |pages=19–28 |doi=10.1016/S1040-6182(00)00074-4 |bibcode=2001QuInt..75...19B }}</ref>
Until the early 1980s, early humans were thought to have been restricted to the African continent in the [[Early Pleistocene]], or until about 0.8 Ma; Hominin migrations outside East Africa were apparently rare in the Early Pleistocene, leaving a fragmentary record of events.<ref name = "Lahr 2010">{{cite book |last=Lahr |first=M. M. |year=2010 |chapter=Saharan Corridors and Their Role in the Evolutionary Geography of 'Out of Africa I' |editor-first=A. |editor-last=Baden |display-editors=etal|title=Out of Africa I: The First Hominin Colonization of Eurasia |publisher=Springer Netherlands |pages=27–46 |isbn=978-90-481-9035-5 }}</ref><ref name="Straus2001">{{cite journal |last1=Straus |first1=L. G. |last2=Bar-Yosef |first2=O. |year=2001 |title=Out of Africa in the Pleistocene: an introduction |journal=Quaternary International |volume=75 |issue=1 |pages=2–4 |doi=10.1016/s1040-6182(00)00071-9|bibcode=2001QuInt..75....1S }}</ref>
==Early dispersals==
{{see|Homo|Oldowan|Homo habilis}}
Pre-''Homo'' hominin expansion out of Africa is suggested by the presence of ''[[Graecopithecus]]'' and ''[[Ouranopithecus]]'', found in Greece and Anatolia and dated to c. 8 million years ago, but these are probably [[Homininae]] but not Hominini. Possibly related are the [[Trachilos footprints]] found in Crete, dated to close to 6 million years ago;<ref>{{Cite journal |last1=Gierliński |first1=Gerard D. |last2=Niedźwiedzki |first2=Grzegorz |last3=Lockley |first3=Martin G. |last4=Athanassiou |first4=Athanassios |last5=Fassoulas |first5=Charalampos |last6=Dubicka |first6=Zofia |last7=Boczarowski |first7=Andrzej |last8=Bennett |first8=Matthew R. |last9=Ahlberg |first9=Per Erik |date=1 October 2017 |title=Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete? |journal=[[Proceedings of the Geologists' Association]] |language=en |volume=128 |issue=5 |pages=697–710 |doi=10.1016/j.pgeola.2017.07.006 |issn=0016-7878|doi-access=free |bibcode=2017PrGA..128..697G |hdl=20.500.12128/3647 |hdl-access=free }}</ref> the age of the footprints was later reestimated to be 6.05 million years ago, 0.35 million years older than previous estimations.<ref>{{Cite journal |last1=Kirscher |first1=Uwe |last2=El Atfy |first2=Haytham |last3=Gärtner |first3=Andreas |last4=Dallanave |first4=Edoardo |last5=Munz |first5=Philipp |last6=Niedźwiedzki |first6=Grzegorz |last7=Athanassiou |first7=Athanassios |last8=Fassoulas |first8=Charalampos |last9=Linnemann |first9=Ulf |last10=Hofmann |first10=Mandy |last11=Bennett |first11=Matthew |last12=Ahlberg |first12=Per Erik |last13=Böhme |first13=Madelaine |date=11 October 2021 |title=Age constraints for the Trachilos footprints from Crete |journal=[[Scientific Reports]] |language=en |volume=11 |issue=1 |page=19427 |doi=10.1038/s41598-021-98618-0 |issn=2045-2322|doi-access=free |pmid=34635686 |pmc=8505496 |bibcode=2021NatSR..1119427K }}</ref> Another reestimation by Willem Jan Zachariasse and Lucas Lourens interpret the purported footprints to have originated 3 million years ago and doubt if they were footprints or the hominins had made the footprints because of the shallow marine setting and the separation of Crete from mainland Greece and Turkey in the Late Pliocene by the South Aegean Basin.<ref>{{Cite journal |last1=Zachariasse |first1=Willem Jan |last2=Lourens |first2=Lucas J. |date=2022-11-02 |title=About the age and depositional depth of the sediments with reported bipedal footprints at Trachilos (NW Crete, Greece) |journal=[[Scientific Reports]] |language=en |volume=12 |issue=1 |page=18471 |doi=10.1038/s41598-022-23296-5 |issn=2045-2322|doi-access=free |pmid=36323766 |pmc=9630425 |bibcode=2022NatSR..1218471Z }}</ref>
''[[Australopithecina]]'' emerged about 5.6 million years ago, in East Africa ([[Afar Depression]]).
[[Gracile australopithecines]] (''[[Australopithecus afarensis]]'') emerged in the same region, around 4 million years ago.
The earliest known retouched tools were found in [[Lomekwi]], Kenya, and date back to 3.3 Ma, in the late [[Pliocene]]. They might be the product of ''[[Australopithecus garhi]]'' or ''[[Paranthropus aethiopicus]]'', the two known hominins contemporary with the tools.<ref>{{cite journal | last1 = Semaw | first1 = S | year = 2000 | title = The World's Oldest Stone Artefacts from Gona, Ethiopia: Their Implications for Understanding Stone Technology and Patterns of Human Evolution Between 2·6–1·5 Million Years Ago | journal = [[Journal of Archaeological Science]] | volume = 27 | issue = 12| pages = 1197–1214 | doi = 10.1006/jasc.1999.0592 | bibcode = 2000JArSc..27.1197S }}</ref> Genus
''[[Homo]]'' is assumed to have emerged by around 2.8 million years ago, with ''[[Homo habilis]]'' being found at [[Lake Turkana]], [[Kenya]]. The delineation of the "human" genus, ''[[Homo]]'', from Australopithecus is somewhat contentious, for which reason the superordinate term "hominin" is often used to include both. "Hominin" technically includes [[Pan (genus)|chimpanzees]] as well as [[Chimpanzee–human last common ancestor|pre-human species]] as old as 10 million years old (the separation of [[Homininae]] into Hominini and [[Gorillini]]).
The earliest known hominin presence outside of Africa dates to close to 2 million years ago. A 2018 study claims evidence for human presence at [[Shangchen]], central China, as early as 2.12 Ma based on [[Magnetostratigraphy|magnetostratigraphic dating]] of the lowest layer containing stone artefacts.<ref name=Zhu2018/>
It has been suggested that ''[[Homo floresiensis]]'' was descended from such an early expansion. It is not clear whether these earliest hominins leaving Africa should be considered ''Homo habilis'', or a form of early ''Homo'' or late ''Australopithecus'' closely related to ''Homo habilis'', or a very early form of ''Homo erectus''. In any case, the morphology of ''H. floresiensis'' has been found to show greatest similarity with ''[[Australopithecus sediba]]'', ''[[Homo habilis]]'' and [[Dmanisi Man]], raising the possibility that the ancestors of ''H. floresiensis'' left Africa before the appearance of ''H. erectus''.<ref>{{Cite journal |author=Dembo, M. |author2=Matzke, N. J. |author3=Mooers, A. Ø. |author4=Collard, M. |title=Bayesian analysis of a morphological supermatrix sheds light on controversial fossil hominin relationships |journal=[[Proceedings of the Royal Society B: Biological Sciences]] |year=2015 |volume=282 |issue=1812 |page=20150943 |doi=10.1098/rspb.2015.0943 |pmid=26202999 |pmc=4528516 }}</ref> A [[Phylogenetic comparative methods|phylogenetic analysis]] published in 2017 suggests that ''H. floresiensis'' was descended from a species (presumably Australopithecine) ancestral to ''[[Homo habilis]]'', making it a "sister species" either to ''H. habilis'' or to a minimally ''habilis''-''erectus''-''ergaster''-''sapiens'' [[clade]], and its line is older than ''H. erectus'' itself. On the basis of this classification, ''H. floresiensis'' is hypothesized to represent a hitherto unknown and very early migration out of Africa, dating to before 2.1 million years ago. A similar conclusion is suggested by the date of 2.1 Ma for the oldest [[Shangchen]] artefacts.<ref name=Zhu2018/>
==''Homo erectus''==
{{see|Oldowan|Acheulean}}
[[File:Carte hachereaux.jpg|thumb|upright=1.5|Map of the distribution of Middle Pleistocene ([[Acheulean]]) [[Cleaver (tool)|cleaver]] finds]]
''[[Homo erectus]]'' emerges just after 2 million years ago.<ref>{{cite journal | last1 = Van Arsdale | first1 = A. P. | year = 2013 | title = Homo erectus – A Bigger, Smarter, Faster Hominin Lineage | journal = Nature Education Knowledge | volume = 4 | issue = 1| page = 2 }}</ref>
Early ''H. erectus'' would have lived face to face with ''H. habilis'' in East Africa for nearly half a million years.<ref>{{cite journal | last1 = Spoor | first1 = F. | last2 = Leakey | first2 = M. G. | last3 = Gathogo | first3 = P. N. | last4 = Brown | first4 = F. H. | last5 = Antón | first5 = S. C. | last6 = McDougall | first6 = I. | last7 = Leakey | first7 = L. N. | year = 2007 | title = Implications of new early Homo fossils from Ileret, east of Lake Turkana, Kenya | journal = [[Nature (journal)|Nature]] | volume = 448 | issue = 7154| pages = 688–691 | doi = 10.1038/nature05986 | pmid = 17687323 | bibcode = 2007Natur.448..688S | s2cid = 35845 }}</ref>
The oldest ''Homo erectus'' fossils appear almost contemporaneously, shortly after two million years ago, both in Africa and in the Caucasus.
The earliest well-dated Eurasian ''H. erectus'' site (if the fossils are indeed ''H. erectus'' — see [[Dmanisi hominins]]) is [[Dmanisi]] in Georgia, securely dated to 1.8 Ma.<ref name="doi10.1073/pnas.1106638108">1.85-1.78 Ma [[95% CI]]. {{Cite journal | last1 = Ferring | first1 = R. | last2 = Oms | first2 = O. | last3 = Agusti | first3 = J. | last4 = Berna | first4 = F. | last5 = Nioradze | first5 = M. | last6 = Shelia | first6 = T. | last7 = Tappen | first7 = M. | last8 = Vekua | first8 = A. | last9 = Zhvania | first9 = D. | last10 = Lordkipanidze | first10 = D. | doi = 10.1073/pnas.1106638108 | title = Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85-1.78 Ma | journal = Proceedings of the National Academy of Sciences | volume = 108 | issue = 26 | pages = 10432–10436 | year = 2011 |pmid= 21646521| pmc = 3127884 | bibcode = 2011PNAS..10810432F| doi-access = free }}</ref><ref name="Garcia 2010">{{cite journal | last1 = Garcia | first1 = T. | last2 = Féraud | first2 = G. | last3 = Falguères | first3 = C. | last4 = de Lumley | first4 = H. | last5 = Perrenoud | first5 = C. | last6 = Lordkipanidze | first6 = D. | year = 2010 | title = Earliest human remains in Eurasia: New 40Ar/39Ar dating of the Dmanisi hominid-bearing levels, Georgia | journal = Quaternary Geochronology | volume = 5 | issue = 4| pages = 443–451 | doi = 10.1016/j.quageo.2009.09.012 | bibcode = 2010QuGeo...5..443G }}</ref> A skull found at Dmanisi is evidence for caring for the old. The skull shows that this ''Homo erectus'' was advanced in age and had lost all but one tooth years before death, and it is perhaps unlikely that this hominid would have survived alone. It is not certain, however, that this is sufficient proof for caring – a partially paralysed chimpanzee at the Gombe reserve survived for years without help.<ref>{{cite journal | last1 = Bauer | first1 = H. R. | year = 1977 | title = Chimpanzee Bipedal Locomotion in the Gombe National Park, East Africa | journal = Primates | volume = 18 | issue = 4| pages = 913–921 | doi=10.1007/bf02382940| s2cid = 41892278 }}</ref>
The earliest known evidence for African ''H. erectus'', dubbed ''[[Homo ergaster]]'', is a
single occipital bone (KNM-ER 2598), described as "H. erectus-like", and dated to about 1.9 Ma (contemporary with ''[[Homo rudolfensis]]''). This is followed by a fossil gap, the next available fossil being [[KNM-ER 3733]], a skull dated to 1.6 Ma.<ref>{{cite journal | last1 = Kimbel | first1 = William H. | last2 = Villmoare | first2 = Brian | year = 2016| title = From Australopithecus to Homo: the transition that wasn't | journal = Philosophical Transactions of the Royal Society B | volume =  371| issue = 1698| page =  20150248| doi = 10.1098/rstb.2015.0248 | pmid = 27298460 | pmc = 4920303 }}</ref>
[[Early Pleistocene]] sites in North Africa, the geographical intermediate of East Africa and Georgia, are in poor stratigraphic context. The earliest of the dated is [[Ain Hanech]] in northern [[Algeria]] (c. 1.8<ref name = "Sahnouni 2002">{{cite journal | last1 = Sahnouni | first1 = M. | last2 = Hadjois | first2 = D. | last3 = van der Made | first3 = J. | last4 = Derradji | first4 = A. Canals | last5 = Medig | first5 = M. | last6 = Belahrech | first6 = H. | last7 = Harichane | first7 = Z. | last8 = Rabhi | first8 = M. | year = 2002 | title = Further research at the Oldowan site of Ain Hanech, North-eastern Algeria | journal = [[Journal of Human Evolution]] | volume = 43 | issue = 6| pages = 925–937 | doi=10.1006/jhev.2002.0608| pmid = 12473489 | bibcode = 2002JHumE..43..925S }}</ref> – 1.2 Ma<ref name = "Geraads 2004">{{cite journal | last1 = Geraads | first1 = D. | last2 = Raynal | first2 = J.-P. | last3 = Eisenmann | first3 = V. | year = 2004 | title = The earliest occupation of North Africa: a reply to Sahnouni ''et al.'' (2002) | url = https://halshs.archives-ouvertes.fr/halshs-00003986/document| journal = Journal of Human Evolution | volume = 46 | issue = 6| pages = 751–761 | doi=10.1016/j.jhevol.2004.01.008| pmid = 15183674 }}</ref>), an [[Oldowan|Oldowan grade]] layer. These sites attest that early ''Homo erectus'' have crossed the North African tracts, which are usually hot and dry.<ref name = "Lahr 2010" />{{rp|2}}
There is little time between ''Homo erectus''' apparent arrival in [[South Caucasus]] around 1.8 Ma, and its probable arrival in East and Southeast Asia. There is evidence of ''H. erectus'' in [[Yuanmou County|Yuanmou]], China, dating to 1.7 Ma and in [[Sangiran]], on [[Java]], Indonesia, from 1.66 Ma.<ref>{{cite journal | last1 = Rightmire | first1 = G. P. | year = 2001 | title = Patterns of hominid evolution and dispersal in the Middle Pleistocene | journal = [[Quaternary International]] | volume = 75 | issue = 1| pages = 77–84 | doi = 10.1016/S1040-6182(00)00079-3 | bibcode = 2001QuInt..75...77R }}</ref>
Ferring et al. (2011) suggest that it was still ''[[Homo habilis]]'' that reached West Asia, and that early ''H. erectus'' developed there. ''H. erectus'' would then have dispersed from West Asia, to East Asia ([[Peking Man]]) Southeast Asia ([[Java Man]]), back to Africa (''[[Homo ergaster]]''), and to Europe ([[Tautavel Man]]).<ref>{{Cite journal | last1 = Ferring | first1 = R. | last2 = Oms | first2 = O. | last3 = Agusti | first3 = J. | last4 = Berna | first4 = F. | last5 = Nioradze | first5 = M. | last6 = Shelia | first6 = T. | last7 = Tappen | first7 = M. | last8 = Vekua | first8 = A. | last9 = Zhvania | first9 = D. | last10 = Lordkipanidze | first10 = D. | doi = 10.1073/pnas.1106638108 | title = Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85-1.78 Ma | journal = Proceedings of the National Academy of Sciences | volume = 108 | issue = 26 | pages = 10432–10436 | year = 2011 | pmid= 21646521| pmc= 3127884 | bibcode = 2011PNAS..10810432F| doi-access = free }}</ref><ref>{{cite journal |doi=10.1016/j.quascirev.2010.04.012|date=June 2011 |last1=Augusti |first1=Jordi |last2=Lordkipanidze |first2=David |title=How "African" was the early human dispersal out of Africa?|volume=30|issue=11–12 |pages=1338–1342 |journal=Quaternary Science Reviews |bibcode=2011QSRv...30.1338A}}</ref>
It appears ''H. erectus'' took longer to move into Europe, the earliest site being [[Barranco León]] in southeastern [[Spain]] dated to 1.4 Ma, associated with ''[[Homo antecessor]]'',<ref name = "Toro-Moyano 2013">{{cite journal | last1 = Toro-Moyano | first1 = I. | last2 = Martínez-Navarro | first2 = B. | last3 = Agustí | first3 = J. | last4 = Souday | first4 = C. | last5 = de Castro | first5 = Bermúdez | last6 = Martinón-Torres | first6 = M. | last7 = Palmqvist | first7 = P. | year = 2013 | title = The oldest human fossil in Europe, from Orce (Spain) | journal = Journal of Human Evolution | volume = 65 | issue = 1| pages = 1–9 | doi = 10.1016/j.jhevol.2013.01.012 | pmid = 23481345 | bibcode = 2013JHumE..65....1T | hdl = 10261/84112 | hdl-access = free }}</ref> and a controversial [[Pirro Nord]] in Southern Italy, allegedly from 1.7 – 1.3 Ma.<ref name = "Arzarello 2007">{{cite journal | last1 = Arzarello | first1 = M. | last2 = Marcolini | first2 = F. | last3 = Pavia | first3 = G. | last4 = Pavia | first4 = M. | last5 = Petronio | first5 = C. | last6 = Petrucci | first6 = M. | last7 = Sardella | first7 = R. | year = 2007 | title = Evidence of earliest human occurrence in Europe: the site of Pirro Nord (Southern Italy) | journal = Die Naturwissenschaften | volume = 94 | issue = 2| pages = 107–112 | doi = 10.1007/s00114-006-0173-3 | pmid = 17061119 | bibcode = 2007NW.....94..107A | s2cid = 42198 }}</ref> The paleobiogeography of early human dispersals in western Eurasia characterizes ''H''. ex gr. ''erectus'' as a temperature sensitive [[stenobiont]], that failed to disperse north of the [[Alpide belt|Alpide Belt]].<ref name=":0">{{Cite journal|title=Paleobiogeography of early human dispersal in western Eurasia: Preliminary results|journal=[[Comptes Rendus Palevol]]|volume=17|issue=4–5|pages=276–286|last=Croitor|first=Roman|doi=10.1016/j.crpv.2017.09.004|year=2018|doi-access=free|bibcode=2018CRPal..17..276C }}</ref> The geographically restricted earliest human presence in the [[Iberian Peninsula]] should be regarded as evidence of a sustainable presence of human population in this isolated area. The [[Pannonian Basin|Pannonian plain]], situated south-west of the [[Carpathian Mountains]], was apparently characterized by a comparatively warm climate similar to that of the [[Mediterranean climate|Mediterranean Area]], while the climate of the western European [[Biogeography#Paleobiogeography|paleobiogeographic]] area was mitigated by [[Gulf Stream]] influence and could support the episodic hominin dispersals toward the [[Iberian Peninsula]].<ref name=":0" /> Apparently, the faunal exchanges between southeastern Europe and the Near East and southern Asia were controlled by the complex interaction of such geographic obstacles as the [[Bosporus]] and the [[Lake Manych-Gudilo|Manych]] Strait, the climate barrier from the north of the [[Greater Caucasus]] range, and the 41 kyr glacial [[Milankovitch cycles]] that repeatedly closed the Bosporus and thus triggered the two-way faunal exchange between [[Southeast Europe|southeastern Europe]] and the [[Near East]], and, apparently, the further westward dispersal of the archaic hominins in Eurasia.<ref>{{Cite journal|title=A Description of Two New Species of the Genus Rucervus (Cervidae, Mammalia) from the Early Pleistocene of Southeast Europe, with Comments on Hominin and South Asian Ruminants Dispersals.|journal=Quaternary|volume=1|issue=2|page=17|last=Croitor|first=Roman|doi=10.3390/quat1020017|year=2018|doi-access=free}}</ref>
By 1 Ma, ''Homo erectus'' had spread across Eurasia (mostly restricted to latitudes south of the [[50th parallel north]]<ref>the northernmost
known Middle Pleistocene site is [[Prehistoric Norfolk|Whithlingham]], at 52.6° N.
Mourre, V., ''Implications culturelles de la technologie des hachereaux'', doctoral thesis, Université de Paris X – Nanterre (2003) Fig. 48 (p. 115).</ref>).
It is hard to say, however, whether settlement was continuous in Western Europe, or if successive waves repopulated the territory in glacial interludes. Early [[Acheulean]] tools at [[Ubeidiya prehistoric site|Ubeidiya]] from 1.4 Ma<ref name = "Martinez-Navarro 2009">{{cite journal | last1 = Martínez-Navarro | first1 = B. | last2 = Belmaker | first2 = M. | last3 = Bar-Yosef | first3 = O. | year = 2009 | title = The large carnivores from 'Ubeidiya (early Pleistocene, Israel): biochronological and biogeographical implications | journal = Journal of Human Evolution | volume = 56 | issue = 5| pages = 514–524 | doi = 10.1016/j.jhevol.2009.02.004 | pmid = 19427671 | bibcode = 2009JHumE..56..514M }}</ref> is some evidence for a continuous settlement in the West, as successive waves out of Africa after then would likely have brought Acheulean technology to Western Europe.{{citation needed|date=February 2016}}
The presence of [[Lower Paleolithic]] human remains in [[List of islands of Indonesia|Indonesian islands]] is good evidence for seafaring by ''Homo erectus'' late in the [[Early Pleistocene]]. Bednarik suggests that navigation had appeared by 1 Ma, possibly to exploit offshore fishing grounds.<ref>{{cite journal | last1 = Bednarik | first1 = R. G. | year = 2001 | title = Replicating the first known sea travel by humans: the Lower Pleistocene crossing of Lombok Strait | journal = Journal of Human Evolution | volume = 16 | issue = 3| pages = 229–242 | doi=10.1007/bf02437414| s2cid = 83823911 }}</ref> He has reproduced a primitive dirigible (steerable) raft to demonstrate the feasibility of faring across the [[Lombok Strait]] on such a device, which he believes to have been done before 850 ka. The strait has maintained a width of at least 20&nbsp;km for the whole of the Pleistocene. Such an achievement by ''Homo erectus'' in the Early Pleistocene offers some strength to the suggested water routes out of Africa, as the [[Strait of Gibraltar|Gibraltar]], [[Strait of Sicily|Sicilian]], and [[Bab-el-Mandeb]] exit routes are harder to consider if watercraft are deemed beyond the capacities of ''Homo erectus''.
==''Homo heidelbergensis''==
Archaic humans in Europe beginning about 0.8 Ma ([[Cleaver (tool)|cleaver-producing]] Acheulean groups)
are classified as a separate, erectus-derived species, known as ''[[Homo heidelbergensis]]''.<ref name="Bar-Yosef, O. 2001"/> ''H. heidelbergensis'' from about 0.4 Ma develops its own characteristic industry, known as [[Clactonian]].
''H. heidelbergensis'' is closely related to ''[[Homo rhodesiensis]]'' (also identified as ''Homo heidelbergensis sensu lato'' or African ''H. heidelbergensis''), known to be present in southern Africa by 0.3 Ma.
''[[Homo sapiens]]'' emerges in Africa before about 0.3 Ma from a lineage closely related to early ''H. heidelbergensis''.<ref name="Callaway 16046">{{cite journal |last=Callaway |first=Ewan |title=Oldest Homo sapiens fossil claim rewrites our species' history |url=http://www.nature.com/news/oldest-homo-sapiens-fossil-claim-rewrites-our-species-history-1.22114 |date=7 June 2017 |journal=[[Nature (journal)|Nature]] |doi=10.1038/nature.2017.22114 |access-date=11 June 2017 }}
{{cite journal |last=Posth |first=Cosimo |display-authors=etal |title=Deeply divergent archaic mitochondrial genome provides lower time boundary for African gene flow into Neanderthals |date=4 July 2017 |journal=[[Nature Communications]] |volume=8 |page=16046 |doi=10.1038/ncomms16046 |pmid=28675384 |pmc=5500885 |bibcode=2017NatCo...816046P }}</ref> The first wave of "[[Out of Africa II]] and "earliest presence of ''H. sapiens'' in West Asia, may date to between .3 and 0.2 Ma,<ref name="Callaway 16046"/> and ascertained for 0.13 Ma.<ref name=pmid21273486>{{cite journal |last1=Armitage |first1=Simon J. |last2=Jasim |first2=Sabah A. |last3=Marks |first3=Anthony E. |last4=Parker |first4=Adrian G. |last5=Usik |first5=Vitaly I. |last6=Uerpmann |first6=Hans-Peter |date=January 2011 |title=The southern route "out of Africa": evidence for an early expansion of modern humans into Arabia |journal=[[Science (journal)|Science]] |volume=331 |issue=6016 |pages=453–456 |pmid=21273486 |doi=10.1126/science.1199113 |bibcode=2011Sci...331..453A |s2cid=20296624 }}</ref> Genetic research also indicates that a later migration wave of ''H. sapiens'' (from .07-.05 Ma) from Africa is responsible for all to most of the ancestry of current non-African populations.<ref>{{cite journal |last1=Pagani |first1=Luca |title=Genomic analyses inform on migration events during the peopling of Eurasia |journal=Nature |date=13 October 2016 |volume=538 |issue=7624 |pages=238–242 |bibcode=2016Natur.538..238P |doi=10.1038/nature19792 |pmid=27654910 |pmc=5164938 }}</ref><ref name="Posth">{{Cite journal|title=Pleistocene Mitochondrial Genomes Suggest a Single Major Dispersal of Non-Africans and a Late Glacial Population Turnover in Europe|journal=Current Biology|volume=26|issue=6|pages=827–833|year=2016|doi = 10.1016/j.cub.2016.01.037
|pmid=26853362|vauthors=Posth C, Renaud G, Mittnik M, Drucker DG, Rougier H, Cupillard C, Valentin F, Thevenet C, Furtwängler A, Wißing C, Francken M, Malina M, Bolus M, Lari M, Gigli E, Capecchi G, Crevecoeur I, Beauval C, Flas D, Germonpré M, van der Plicht J, Cottiaux R, Gély B, Ronchitelli A, Wehrberger K, Grigorescu D, Svoboda J, Semal P, Caramelli D, Bocherens H, Harvati K, Conard NJ, Haak W, Powell A, Krause J|bibcode=2016CBio...26..827P |hdl=2440/114930|s2cid=140098861|hdl-access=free}}</ref><ref name="ReferenceC">{{cite journal | vauthors = Haber M, Jones AL, Connel BA, Asan, Arciero E, Huanming Y, Thomas MG, Xue Y, Tyler-Smith C | title = A Rare Deep-Rooting D0 African Y-chromosomal Haplogroup and its Implications for the Expansion of Modern Humans Out of Africa | journal = Genetics | volume = 212 | issue = 4 | pages = 1421–1428 | date = June 2019 | pmid = 31196864 | pmc = 6707464 | doi = 10.1534/genetics.119.302368 }}</ref>
==Routes out of Africa==
Most attention as to the route taken from Africa to West Asia is given to the [[Levantine corridor|Levantine land corridor]] and the [[Bab-el-Mandeb]] straits. The latter separates the Horn of Africa and Arabia, and may have allowed dry passage during some periods of the Pleistocene. Another candidate is the [[Strait of Gibraltar]]. A route across the [[Strait of Sicily]] was suggested in the 1970s but is now considered unlikely.
===Levantine corridor===
The use by hominins of the [[Levantine corridor]], connecting [[Egypt]] via the [[Sinai peninsula]] with the [[Eastern Mediterranean]], has been associated to the phenomenon of rising and declining humidity of the desert belt of northern Africa, known as the [[Sahara pump]]. The numerous hominin sites in the Levant, such as [[Ubeidiya prehistoric site|Ubeidiya]] and [[Misliya cave]], are used as indicators of this migration route.{{citation needed|date=January 2020}} As of 2012, the genetic analysis of human populations in Africa and Eurasia supports the concept that during the [[Paleolithic]] and [[Mesolithic]] periods, this route was more important for bi-directional human migrations between Africa and Eurasia than was the Horn of Africa.<ref>[http://hpgl.stanford.edu/publications/AJHG_2004_v74_p000-0130.pdf J. R. Luis ''et al.'', "The Levant versus the Horn of Africa: Evidence for Bidirectional Corridors of Human Migrations"] {{webarchive|url=https://web.archive.org/web/20120216123633/http://hpgl.stanford.edu/publications/AJHG_2004_v74_p000-0130.pdf |date=2012-02-16 }}, ''[[American Journal of Human Genetics]]'', 74: 532-544.</ref>
===Horn of Africa to Arabia (Bab el-Mandeb)===
[[File:Bab el Mandeb NASA with description.jpg|thumb|upright=1.2|Bab-el-Mandeb strait]]
[[Bab-el-Mandeb]] is a 30&nbsp;km strait between East Africa and the Arabian Peninsula, with a small island, [[Perim]], 3&nbsp;km off the Arabian bank. The strait has a major appeal in the study of Eurasian expansion in that it brings East Africa close to Eurasia. It does not require hopping from one water body to the next across the North African desert.{{citation needed|date=March 2016}}
The land connection with Arabia disappeared in the [[Pliocene]],<ref>{{cite journal | last1 = Redfield | first1 = T. F. | last2 = Wheeler | first2 = W. H. | last3 = Often | first3 = M. | year = 2003 | title = A kinematic model for the development of the Afar depression and its paleogeographic implications | journal = Earth and Planetary Science Letters | volume = 216 | issue = 3| pages = 383–398 | doi=10.1016/s0012-821x(03)00488-6 | bibcode=2003E&PSL.216..383R}}</ref> and though it may have briefly reformed,{{when|date=September 2018}}<ref>{{cite journal | last1 = Haq | first1 = B. U. | last2 = Hardenbol | first2 = J. | last3 = Vail | first3 = P. R. | year = 1987 | title = Chronology of fluctuating sea levels since the Triassic | journal = Science | volume = 235 | issue = 4793| pages = 1156–1167 | doi = 10.1126/science.235.4793.1156 | pmid = 17818978 | bibcode = 1987Sci...235.1156H | s2cid = 24673686 }}</ref> the evaporation of the Red Sea and associated increase in salinity would have left traces in the fossil record after just 200 years and [[evaporite]] deposits after 600 years. Neither have been detected.<ref>{{cite journal | last1 = Fernandes | first1 = C. A. | last2 = Rohling | first2 = E. J. | last3 = Siddall | first3 = M. | year = 2006 | title = Absence of post-Miocene Red Sea land bridges: biogeographic implications | journal = Journal of Biogeography | volume = 33 | issue = 6| pages = 961–966 | doi = 10.1111/j.1365-2699.2006.01478.x | doi-access = free | bibcode = 2006JBiog..33..961F }}</ref> A strong current flows from the Red Sea into the Indian Ocean and crossing would have been difficult without a land connection.
Oldowan grade tools are reported from Perim Island,<ref>Chauhan, P. R. (2009). "Early Homo Occupation Near the Gate of Tears: Examining the Paleoanthropological Records of Djibouti and Yemen", in: E. Hover and D.R. Braun (Eds.) ''Interdisciplinary Approaches to the Oldowan'', Springer Netherlands, 49–59. {{doi|10.1007/978-1-4020-9059-2}}</ref> implying that the strait could have been crossed in the Early Pleistocene, but these finds have yet to be confirmed.<ref>{{cite journal | last1 = Groucutt | first1 = H. S. | last2 = Petraglia | first2 = M. D. | year = 2012 | title = The prehistory of the Arabian peninsula: deserts, dispersals, and demography | journal = Evolutionary Anthropology | volume = 21 | issue = 3| pages = 113–125 | doi = 10.1002/evan.21308 | pmid = 22718479 | s2cid = 13705573 }}</ref>
===Strait of Gibraltar===
The [[Strait of Gibraltar]] is the Atlantic entryway to the Mediterranean, where Spanish and Moroccan banks are only 14&nbsp;km apart. A decrease in [[sea levels]] in the Pleistocene due to [[Glacial period|glaciation]] would not have brought this down to less than 10&nbsp;km. Deep currents push westwards, and surface water flows strongly back into the Mediterranean.
Entrance into Eurasia across the strait of Gibraltar could explain the hominin remains at [[Barranco León]] in southeastern Spain (1.4 Ma)<ref name = "Toro-Moyano 2013" /> and [[Atapuerca Mountains#Sima del Elefante (1996-)|Sima del Elefante]] in northern Spain (1.2 Ma).<ref>{{cite journal | last1 = Carbonell | first1 = E. J. M. | last2 = Bermudez de Castro | first2 = J. L. A. | last3 = Allue | first3 = E. | last4 = Bastir | first4 = M. | last5 = Benito | first5 = A. | last6 = Caceres | first6 = I. | last7 = Verges | first7 = J. M. | year = 2005 | title = An Early Pleistocene hominin mandible from Atapuerca-TD6, Spain | journal = Proceedings of the National Academy of Sciences | volume = 102 | issue = 16| pages = 5674–5678 | doi=10.1073/pnas.0501841102| pmid = 15824320 | pmc = 556125 | bibcode = 2005PNAS..102.5674C | doi-access = free }}</ref><ref>{{cite journal | last1 = Carbonell | first1 = E. | last2 = Bermúdez de Castro | first2 = J. M. | last3 = Parés | first3 = J. M. | last4 = Pérez-González | first4 = A. | last5 = Cuenca-Bescós | first5 = G. | last6 = Ollé | first6 = A. | last7 = Arsuaga | first7 = J. L. | year = 2008 | title = The first hominin of Europe | url = https://deepblue.lib.umich.edu/bitstream/2027.42/62855/1/nature06815.pdf| journal = Nature | volume = 452 | issue = 7186| pages = 465–469 | doi = 10.1038/nature06815 | pmid = 18368116 | hdl = 2027.42/62855 | bibcode = 2008Natur.452..465C | s2cid = 4401629 | hdl-access = free }}</ref> But the site of Pirro Nord in southern Italy, allegedly from 1.3 – 1.7 Ma,<ref name = "Arzarello 2007" /> suggests a possible arrival from the East. Resolution is insufficient to settle the matter.<ref name = "Straus2001" />
===Strait of Sicily===
Passage across the [[Strait of Sicily]] was suggested by [[Henriette Alimen|Alimen]] (1975)<ref>Alimen, H. (1975). "Les 'Isthmes' hispano-marocain et Sicilo-Tunisien aux temps Acheuléens". ''L'Anthropologie'', 79, 399–436.</ref> based on the 1973 discovery of Oldowan grade tools in Sicily.<ref>Bianchini, G. (1973). "Gli 'hacheraux' nei giacimenti paleolitici della Sicilia sud occidentale". ''Proceedings of the XV Scientific Meeting of the Italian Institute of Prehistory and Protohistory'', 11–25 October 1972.</ref>
Radiometric dates, however, have not been produced, and the artefacts might as well be from the Middle Pleistocene,<ref>{{cite journal | last1 = Villa | first1 = P | year = 2001 | title = Early Italy and the colonization of Western Europe | journal = Quaternary International | volume = 75 | issue = 1 | pages = 113–130 | doi=10.1016/s1040-6182(00)00083-5| bibcode = 2001QuInt..75..113V }}</ref>
and it is unlikely that there was a land bridge during the Pleistocene.<ref name = "Lahr 2010" />{{rp|3}}
==Causes for dispersal==
===Climate change and hominin flexibility===
For a given species in a given environment, available resources will limit the number of individuals that can survive indefinitely.
This is the [[carrying capacity]]. Upon reaching this threshold, individuals may find it easier to gather resources in the poorer yet less exploited peripheral environment than in the preferred habitat. ''Homo habilis'' could have developed some baseline behavioural flexibility prior to its expansion into the peripheries (such as encroaching into the predatory guild<ref>{{cite journal | last1 = Brantingham | first1 = P. J. | s2cid = 2930029 | year = 1998 | title = Hominid–Carnivore Coevolution and Invasion of the Predatory Guild | journal = Journal of Anthropological Archaeology | volume = 17 | issue = 4| pages = 327–353 | doi = 10.1006/jaar.1998.0326 }}</ref><ref>Lewis, M. E., & Werdelin, L. (2007). "Patterns of change in the Plio-Pleistocene carnivorans of eastern Africa: Implications for hominin Evolution". In R. Bobe, Z. Alemseged, & A. K. Behrensmeyer (Eds.), ''Hominin environments in the East African Pliocene: An assessment of the faunal evidence''. Springer, 77–106.</ref>). This flexibility could then have been positively selected and amplified, leading to ''Homo erectus''{{'}} adaptation to the peripheral open habitats.<ref>{{cite journal | last1 = Marean | first1 = C. W. | year = 1989 | title = Sabertooth cats and their relevance for early hominid diet and evolution | journal = Journal of Human Evolution | volume = 18 | issue = 6| pages = 559–558 | doi = 10.1016/0047-2484(89)90018-3 | bibcode = 1989JHumE..18..559M }}</ref> A new and environmentally flexible hominin population could have come back to the old niche and replaced the ancestral population.<ref>{{cite journal | last1 = Eldredge | first1 = N. | last2 = Gould | first2 = S. J. | year = 1997 | title = On Punctuated Equilibria | journal = Science | volume = 276 | issue = 5311| pages = 337–341 | doi = 10.1126/science.276.5311.337c | pmid = 9139351 }}</ref> Moreover, some step-wise shrinking of the woodland and the associated reduction of hominin carrying capacity in the woods around 1.8 Ma, 1.2 Ma, and 0.6 Ma would have stressed the carrying capacity's pressure for adapting to the [[Open terrain|open grounds]].<ref>{{cite journal | last1 = Potts | first1 = R | title = Evolution and climate variability| year = 1996 | journal = Science | volume = 273 | issue = 5277| pages = 922–923 | doi=10.1126/science.273.5277.922| bibcode = 1996Sci...273..922P | s2cid = 129580598 }}</ref><ref>{{cite journal | last1 = Cerling | first1 = T.E. | last2 = Harris | first2 = J.M. | last3 = MacFadden | first3 = B.J. | last4 = Leakey | first4 = M.G. | last5 = Quade | first5 = J. | last6 = Eisenmann | first6 = V. | last7 = Erleringer | first7 = J.R. | year = 1997 | title = Global vegetation change through the Miocene/Pliocene boundary | journal = Nature | volume = 389 | issue = 6647| pages = 153–158 | doi=10.1038/38229 | bibcode = 1997Natur.389..153C| s2cid = 4400133 | url = http://doc.rero.ch/record/13396/files/PAL_E199.pdf }}</ref> With ''Homo erectus''{{'}} new environmental flexibility, favourable climate fluxes likely opened it the way to the Levantine corridor, perhaps sporadically, in the Early Pleistocene.<ref name = "Lahr 2010" /> There is [[evidence]] that the [[Mid-Pleistocene Transition|Mid-Pleistocene Revolution]] facilitated mammalian turnovers during the Late Early and Early Middle Pleistocene that may have included the hominin dispersals observed in the [[Fossil|fossil record]] around this time.<ref>{{Cite journal |last=Palombo |first=Maria Rita |date=28 February 2017 |title=Discrete dispersal bioevents of large mammals in Southern Europe in the post-Olduvai Early Pleistocene: A critical overview |url=https://linkinghub.elsevier.com/retrieve/pii/S104061821500806X |journal=[[Quaternary International]] |language=en |volume=431 |pages=3–19 |doi=10.1016/j.quaint.2015.08.034 |bibcode=2017QuInt.431....3P |access-date=19 March 2024 |via=Elsevier Science Direct}}</ref>
===Chasing fauna===
[[Lithic analysis]] implies that Oldowan hominins were not predators.<ref>Shipman, P. A. T. (1984). Hunting in Early Hominids: Theoretical Framework and Tests, 27–43.</ref> However, ''Homo erectus'' appears to have followed animal migrations to the north during wetter periods, likely as a source of scavenged food. The sabre-tooth cat ''[[Megantereon]]'' was an [[apex predator]] of the Early and Middle Pleistocene (before [[Marine Isotope Stage|MIS]] 12). It became extinct in Africa c. 1.5 Ma,<ref>{{cite journal | last1 = Arribas | first1 = A. | last2 = Palmqvist | first2 = P. | year = 1999 | title = On the Ecological Connection Between Sabre-tooths and Hominids: Faunal Dispersal Events in the Lower Pleistocene and a Review of the Evidence for the First Human Arrival in Europe | journal = Journal of Archaeological Science | volume = 26 | issue = 5| pages = 571–585 | doi = 10.1006/jasc.1998.0346 | bibcode = 1999JArSc..26..571A }}</ref> but had already moved out through the Sinai, and is among the faunal remains of the [[Levant]]ine hominin site of [[Ubeidiya prehistoric site|Ubeidiya]], c. 1.4 Ma.<ref name = "Martinez-Navarro 2009" /> It could not break [[bone marrow]] and its kills were likely an important food source for hominins,<ref>Lewis, M.E., Werdelin, L. (2010). "Carnivoran Dispersal Out of Africa During the Early Pleistocene: Relevance for Hominins?". In: A. Baden et al. (Eds.), ''Out of Africa I: The First Hominin Colonization of Eurasia''. Springer Netherlands, pp. 13-26.</ref> especially in glacial periods.<ref>{{cite journal | last1 = Turner | first1 = A | year = 1999 | title = Assessing earliest human settlement of Eurasia: Late Pliocene dispersions from Afric | journal = Antiquity | volume = 73 | issue = 281| pages = 563–570 | doi=10.1017/s0003598x0006511x| s2cid = 162093694 }}</ref> According to this hypothesis, hominins would also have successfully competed with the [[Kleptoparasitism|kleptoparasitic]] giant short-faced hyena, ''[[Pachycrocuta]]'', for these carcasses.<ref>{{Cite journal |last1=Rodríguez |first1=Jesús |last2=Hölzchen |first2=Ericson |last3=Caso-Alonso |first3=Ana Isabel |last4=Berndt |first4=Jan Ole |last5=Hertler |first5=Christine |last6=Timm |first6=Ingo J. |last7=Mateos |first7=Ana |date=28 September 2023 |title=Computer simulation of scavenging by hominins and giant hyenas in the late Early Pleistocene |journal=[[Scientific Reports]] |language=en |volume=13 |issue=1 |pages=14283 |doi=10.1038/s41598-023-39776-1 |pmid=37770511 |issn=2045-2322 |pmc=10539305 |bibcode=2023NatSR..1314283R }}</ref> In colder Eurasian times, the hominin diet would have to be principally meat-based and Acheulean hunters must have competed with cats.{{citation needed|date=March 2016}}
Some papers have argued against this hypothesis, showing that the dispersals of hominins from Africa into Eurasia were asynchronous with those of other land mammals and that the latter was thus unlikely to be the cause of the former.<ref>{{Cite journal |last1=O'Regan |first1=H. J. |last2=Turner |first2=A. |last3=Bishop |first3=L. C. |last4=Elton |first4=S. |last5=Lamb |first5=A. L. |date=1 June 2011 |title=Hominins without fellow travellers? First appearances and inferred dispersals of Afro-Eurasian large-mammals in the Plio-Pleistocene |url=https://www.sciencedirect.com/science/article/pii/S0277379109004016 |journal=[[Quaternary Science Reviews]] |series=Early Human Evolution in the Western Palaearctic: Ecological Scenarios |volume=30 |issue=11 |pages=1343–1352 |doi=10.1016/j.quascirev.2009.11.028 |bibcode=2011QSRv...30.1343O |issn=0277-3791 |access-date=5 February 2024 |via=Elsevier Science Direct}}</ref><ref>{{Cite journal |last=Palombo |first=Maria Rita |date=8 May 2013 |title=What about causal mechanisms promoting early hominin dispersal in Eurasia? A research agenda for answering a hotly debated question |url=https://linkinghub.elsevier.com/retrieve/pii/S1040618211007051 |journal=[[Quaternary International]] |language=en |volume=295 |pages=13–27 |doi=10.1016/j.quaint.2011.12.019 |bibcode=2013QuInt.295...13P |access-date=26 March 2024 |via=Elsevier Science Direct}}</ref>
===Coevolved zoonotic diseases===
[[Ofer Bar-Yosef|Bar-Yosef]] and Belfer-Cohen<ref name="Bar-Yosef, O. 2001"/> suggest that the success of hominins within Eurasia once out of Africa is in part due to the absence of [[Zoonosis|zoonotic diseases]] outside their original habitat. Zoonotic diseases are those that are transmitted from animals to humans. While a disease specific to hominins must keep its human host alive long enough to transmit itself, zoonotic diseases will not necessarily do so as they can complete their life cycle without humans. Still, these infections are well accustomed to human presence, having evolved alongside them. The higher an African ape's population density, the better a disease fares. 55% of chimps at the [[Gombe Stream National Park|Gombe reserve]] die of disease, most of them zoonotic.<ref>Goodall, J., (1986). ''The Chimpanzees of Gombe: Patterns of Behavior''. Belknap Press of Harvard University Press, Cambridge, MA.</ref> The majority of these diseases are still restricted to hot and damp African environments. Once hominins had moved out into drier and colder habitats of higher latitudes, one major limiting factor in population growth was out of the equation.
===Physiological traits===
While ''Homo habilis'' was certainly bipedal, its long arms are indicative of an arboreal adaptation.<ref>{{cite journal | last1 = Ruff | first1 = C | year = 2009 | title = Relative limb strength and locomotion in ''Homo habilis'' | journal = American Journal of Physical Anthropology | volume = 138 | issue = 1| pages = 90–100 | doi = 10.1002/ajpa.20907 | pmid = 18711733 }}</ref> ''Homo erectus'' had longer legs and shorter arms, revealing a transition to obligate terrestriality, though it remains unclear how this change in relative leg length might have been an advantage.<ref>{{cite journal | last1 = Steudel | first1 = K | year = 1996 | title = Limb morphology, bipedal gait, and the energetics of hominid locomotion | journal = American Journal of Physical Anthropology | volume = 99 | issue = 2| pages = 345–355 | doi = 10.1002/(SICI)1096-8644(199602)99:2<345::AID-AJPA9>3.0.CO;2-X | pmid = 8967332 }}</ref> Sheer body size, on the other hand, seems to have allowed for better walking [[Efficient energy use|energy efficiency]] and [[endurance]].<ref>{{cite journal | last1 = Steudel | first1 = K. L. | year = 1994 | title = Locomotor energetics and hominid evolution | journal = Evolutionary Anthropology: Issues, News, and Reviews | volume = 3 | issue = 2| pages = 42–48 | doi = 10.1002/evan.1360030205 | s2cid = 85387559 }}</ref> A larger ''Homo erectus'' would also [[dehydration|dehydrate]] more slowly and could thus cover greater distances before facing [[Thermoregulation|thermoregulatory]] limitations.<ref>{{cite journal | last1 = Wheeler | first1 = P. E. | year = 1992 | title = The thermoragulatory advantages of large body size for hominids foraging in Savannah environments | journal = Journal of Human Evolution | volume = 23 | issue = 4| pages = 351–362 | doi=10.1016/0047-2484(92)90071-g| bibcode = 1992JHumE..23..351W }}</ref> The ability for prolonged walking at a normal pace would have been a decisive factor for effective colonisation of Eurasia.<ref>Klein, R. G. (1999). ''The human career: Human biological and human origins'', (2nd ed.). Chicago: Chicago University Press. 249-250.</ref>
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====Brain thermoregulation====
{{off topic|date=August 2018}} the material below is completely detached from the "Out of Africa" topic, and appears to be concerned with the question of physiological changes related to a "move into open grasslands", perhaps related to early dispersal within Africa
{{merge|Homo|date=August 2018}}
Thermoregulation and dehydration are major problems that need to be dealt with to move into the open grasslands. In particular, [[Angiogenesis|vascularisation]] of the brain is crucial in maintaining it in the narrow frame of tolerable temperatures.
Bones of the higher cranium grow in response to expansion of cerebral mass, in such a way that brain tissue and [[blood vessel]]s mold the inner brain case. [[Endocast|Endocranial casts]] of fossil skulls allow approximating brain vascularisation.<ref>Bruner, E. (2003). "Fossil traces of the human thought: paleoneurology and the evolution of the genus ''Homo''". ''Rivista di Antropologia'' [''Journal of Anthropological Sciences''], 81, 29–56.</ref> [[Dean Falk]] noticed that a single large vessel, the occipital marginal sinus, was responsible for irrigating most of the brain in early [[Australopithecines|australopiths]] (''[[Australopithecus afarensis]]'', ''[[Paranthropus robustus]]'' and ''[[Paranthropus boisei|boisei]]'').<ref>{{cite journal | last1 = Falk | first1 = D | year = 1986 | title = Evolution of cranial blood drainage in hominids: enlarged occipital/marginal sinuses and emissary foramina | journal = American Journal of Physical Anthropology | volume = 70 | issue = 3| pages = 311–324 | doi = 10.1002/ajpa.1330700306 }}</ref> The vessel grew smaller with time to be progressively replaced by a network of small veins in later hominins, starting with ''Homo habilis'' and continuing well into Eurasia. She interprets the change as an adaptation to cool the brain,<ref>Falk, D. (1988). "Enlarged occipital/marginal sinuses and emissary foramina: Their significance in hominid evolution". In: ''The evolutionary history of the "robust" australopithecines'' (eds. F. Grine. Aldine).</ref> which she uses to advance her "[[radiator theory]]" for accelerated [[encephalisation]] from ''Homo habilis'' onwards.<ref>{{cite journal | last1 = Falk | first1 = D | year = 1990 | title = Brain evolution in Homo: The 'radiator' theory | journal = Behavioral and Brain Sciences | volume = 13 | issue = 2| pages = 333–381 | doi = 10.1017/S0140525X00078973 }}</ref> To Falk, [[bipedalism]], which predates large brains, favoured a rewiring of [[Cerebral blood flow|cerebral blood vessels]] into a gravity-assisted irrigation network, itself allowing the cool down needed for encephalisation.
Endocranial casts of ''Homo habilis'' and ''Homo erectus'' differ in the organisation of the [[frontal lobe]], in particular in the [[prefrontal cortex]] where higher mental functions of [[consciousness]] and [[abstraction]] occur.<ref>Holloway, R. L., Sherwood, C. C., Hof, P. R., & Rilling, J. K. (2009). "Evolution of the Brain in Humans – Paleoneurology". In ''Encyclopedia of Neuroscience'', 1326-1338.</ref> By themselves, mental capacities have likely played a role in the success of Eurasian colonisation. They would have allowed for greater [[social complexity]],<ref>{{cite journal | last1 = O'Connell | first1 = J. F. | last2 = Hawkes | first2 = K. | last3 = Jones | first3 = N. G. B. | year = 1999 | title = Grandmothering and the evolution of Homo erectus | journal = Journal of Human Evolution | volume = 36 | pages = 461–485 | doi=10.1006/jhev.1998.0285 | pmid = 10222165}}</ref> predation and sharing prey,<ref>{{cite journal | last1 = Stanford | first1 = C.B. | year = 1998 | title = The social behavior of chimpanzees and bonobos: empirical evidence and shifting assumptions | journal = Current Anthropology | volume = 39 | pages = 399–420 | doi=10.1086/204757}}</ref> and an overall higher quality [[diet (nutrition)|diet]].<ref>{{cite journal | last1 = Aiello | first1 = L.C. | last2 = Wheeler | first2 = P. | year = 1995 | title = Expensive-tissue hypothesis: the brain and digestive system in human and primate evolution | journal = Current Anthropology | volume = 36 | pages = 199–221 | doi = 10.1086/204350 }}</ref>
According to Wheeler,<ref>{{cite journal | last1 = Wheeler | first1 = P. E. | year = 1985 | title = The Loss of Functional Body Hair in Man: the Influence of Thermal Environment, Body Form and Bipedality | journal = Journal of Human Evolution | volume = 14 | issue = 1| pages = 23–28 | doi = 10.1016/S0047-2484(85)80091-9 }}</ref> loss of functional [[Androgenic hair|body hair]] would have helped prevent [[hyperthermia]], since hair will obstruct air flow over the skin and restrict cooling by [[evaporation]]. He further suggests that body cooling due to hair loss has relieved a thermal constraint on brain size (but in a response to Falk's radiator hypothesis, [[Ralph Holloway]] maintains that there is no evidence for a temperature constraint on brain size<ref>{{cite journal | last1 = Holloway | first1 = R. L. | year = 1990 | title = Falk's radiator hypothesis | journal = Behavioral and Brain Sciences | volume = 13 | issue = 2| page = 360 | doi = 10.1017/S0140525X00079139 }}</ref>).
It remains unclear whether hair loss was part of human [[adaptation]] or [[preadaptation]] to Eurasia.{{cn|date=August 2018}}
-->
== Effects ==
The appearance of early hominins in Eurasia coincided with a reduction in the diversity of the continent's carnivore guild. It has been postulated that this was related to the Oldowan-Acheulean transition, as the development of Acheulean technology signifies a change in human ecology from a passive, scavenging role to that of more active predation.<ref>{{Cite journal |last1=Rodríguez-Gómez |first1=Guillermo |last2=Martín-González |first2=Jesús A. |last3=Espigares |first3=M. Patrocinio |last4=Bermúdez de Castro |first4=José María |last5=Martínez-Navarro |first5=Bienvenido |last6=Arsuaga |first6=Juan Luis |last7=Palmqvist |first7=Paul |date=15 March 2024 |title=From meat availability to hominin and carnivore biomass: A paleosynecological approach to reconstructing predator-prey biomass ratios in the Pleistocene |journal=[[Quaternary Science Reviews]] |language=en |volume=328 |pages=108474 |doi=10.1016/j.quascirev.2023.108474 |doi-access=free }}</ref>
==See also==
* [[Archaic humans in Southeast Asia]]
* [[Archaic humans]]
* [[Interbreeding between archaic and modern humans]]
==References==
{{reflist|colwidth=30em}}
==Further reading==
* {{citation|last1=Antón|first1=Susan C.|last2=Swisher|first2=Carl C. III|year=2004|title=Early Dispersals of ''Homo'' from Africa|journal=Annual Review of Anthropology|pages=271–296|volume=33|doi=10.1146/annurev.anthro.33.070203.144024|postscript=.|ref=none}}
* {{citation|author1=Eudald Carbonell|author2=Marina Mosquera|author3=Xosé Pedro Rodríguez|author4= José María Bermúdez de Castro|author5= Francesc Burjachs|author6=Jordi Rosell|author7=Robert Sala|author8=Josep Vallverdú|year=2008|title=Eurasian Gates: The Earliest Human Dispersals|jstor=20371223|others={{subscription required}}|journal=Journal of Anthropological Research|pages=195–228|volume=64|issue=2|ref={{harvid|Carbonell et al.|2008}}|postscript=.|doi=10.3998/jar.0521004.0064.202|s2cid=85227705}}
* {{citation|last=Ciochon|first=Russell L.|year=2010|chapter=Divorcing Hominins from the ''Stegodon–Ailuropoda'' Fauna: New Views on the Antiquity of Hominins in Asia|title=Out of Africa I: The First Hominin Colonization of Eurasia|series=Vertebrate Paleobiology and Paleoanthropology Series|editor=John G. Fleagle|display-editors=etal|location=Dordrecht|pages=111–126|publisher=Springer|isbn=978-90-481-9035-5|postscript=. |doi=10.1007/978-90-481-9036-2_8|ref=none}} {{ISBN|978-90-481-9036-2}} (online).
* {{citation|last=Dennell|first=Robin|year=2009|title=The Palaeolithic Settlement of Asia|series=Cambridge World Archaeology|location=Cambridge|publisher=Cambridge University Press|isbn=978-0-521-84866-4|postscript=. |ref=none}} {{ISBN|978-0-521-61310-1}} (paperback).
* {{citation|last=Dennell|first=Robin|year=2010|chapter='Out of Africa I': Current Problems and Future Prospects|title=Out of Africa I: The First Hominin Colonization of Eurasia|series=Vertebrate Paleobiology and Paleoanthropology Series|editor=John G. Fleagle|display-editors=etal|location=Dordrecht|pages=247–274|publisher=Springer|isbn=978-90-481-9035-5|postscript=. |doi=10.1007/978-90-481-9036-2_15|ref=none
|oclc=762628720}}
* {{Citation|last=Rabett|first=Ryan J.|year=2012|title=Human Adaptation in the Asian Palaeolithic: Hominin Dispersal and Behaviour during the Late Quaternary|url=https://books.google.com/books?id=coFA6_r4PTUC|location=Cambridge|publisher=Cambridge University Press|isbn=978-1-107-01829-7|postscript=.|ref=none}}
* {{citation|last=Zaim|first=Yahdi|year=2010|chapter=Geological Evidence for the Earliest Appearance of Hominins in Indonesia|title=Out of Africa I: The First Hominin Colonization of Eurasia|series=Vertebrate Paleobiology and Paleoanthropology Series|editor=John G. Fleagle|display-editors=etal|location=Dordrecht|pages=97–110|publisher=Springer|isbn=978-90-481-9035-5|postscript=. |doi=10.1007/978-90-481-9036-2_7|ref=none}} {{ISBN|978-90-481-9036-2}} (online).
{{Early human migrations}}
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[[Category:Archaeological theory]]
[[Category:Homo erectus]]
[[Category:Peopling of the world]]
[[Category:Prehistoric migrations]]
[[Category:History of Africa]]