Coastal migration

Water helped in the distribution of humanity across the face of the planet: along seashores, lake margins and river banks. This would have accounted for the prehistoric peopling of most of the Old World, from Africa to Europe and mainland Asia. Strolling or swimming along the beach would have been sufficient to carry mankind from the Horn of Africa to the Peloponnesos, from the Levant to the Korean Peninsula, from Singapore to Siberia. When much water was bound up on land as glaciers in the Ice Ages, sea levels were lower than they are today, and previously submerged land-bridges appeared. At such times, it would have been possible to walk dry-shod from Tripoli and Tunisia to Malta and Sicily, from South Korea to South Japan, and from the Sakhalin Peninsula to Hokkaido, North Japan, from Malaysia to Sumatra, Java and Bali. These temporary land-bridges helped the spread of humans into vast new areas of the Earth.

Between Siberia and Alaska there was a broad land-connection known as Beringia: it was more than a ‘bridge’ as it was over 500 kilometers wide, from its northern to its southern shore. Deepsea corings show that this dry land connection between Asia and America appeared and disappeared (with falls and rises of the sea level) many times over the last few hundred thousand years. The southern flank of Beringia must have had a mild and balmy climate, because the land connection cut off the icy Arctic current to the North, while the warm Japan current played upon the South coast.
Beachcombers would have had a tolerable life on the southern flank and that was the path they probably took to people the New World, perhaps originally more than 100 thousands of years ago (ka) and probably on several excursions.

At some stages and in some places, humans learned to cross the water, even without a land-bridge. Java and Bali were periodically connected to the Asian mainland, so that animals, including humans, could easily gain access to them. However, the Indonesian island of Flores, part of what was named Wallacia (after Alfred Russel Wallace), could be reached only by sea crossings, even when the sea level was at its lowest. Yet stone tools and fossil bones on Flores show that humans (probably Homo erectus) and archaic elephants (Stegodon) must have crossed this deep oceanic channel 0.9 to 0.8 Ma [1, 2]. We have no evidence to suggest that they knew how to make boats so early. Either they floated across using tree trunks, rafts of detached vegetation, or logs, or they paddled holding floats, or they swam. Somehow or other, humans could cross a stretch of water, which, at lowest sea level, was 19-20 kilometers wide nearly a million years ago [3-6]. Morwood et al. [1, 2] have concluded that Homo erectus was capable of repeated water crossings using water-craft, by the beginning of the middle Pleistocene, 0.7-0.9 Ma.

How the upright ape conquered the world
Some 6 million years ago we split from a common ancestor with chimps. Fossils found at the key sites shown on the map below reveal that hominins then diversified into many species and spread far from their ancestral home in Africa. Click on each site to learn more about what we've found there. https://www.newscientist.com/article/human-evolution-map/

The Continental Shelf Hypothesis

We attempt to reconstruct the evolutionary history of apes and humans by using the available biomolecular, geological, fossil and comparative data. Our hypothesis is that wading-climbing hominids in coastal forests near the Arabian peninsula evolved during the Ice Ages into wading-diving Homo species along the Indian Ocean.[pdf]

Possible Migration Route Of Homo Erectus From Africa Discovered

"We have found 500,000 years old traces of the presence of Homo erectus - a total of more than a thousand stone products including characteristic hand axes, which proves the existence of a previously unknown migration route of this species beyond the African continent, probably along Red Sea coasts", says the research project leader Prof. Miroslaw Masojc from the Institute of Archaeology, University of Wroclaw. He adds that these are by far the oldest traces of human presence in this part of North-East Africa.

Up to now, the prevailing views were that H. erectus moved north mainly along the Nile Valley. The researcher adds that although today the study area is a flat and inhospitable desert, hundreds of thousands of years ago there were periods of a much more humid climate. There was vegetation and rivers - their dried beds indicate the course towards the north-east, towards the Red Sea.

Saharan green corridors and Middle Pleistocene hominin dispersals across the Eastern Desert, Sudan

The Sahara Desert episodically became a space available for hominins in the Pleistocene. Mostly, desert conditions prevailed during the interpluvial periods, which were only periodically interrupted by enhanced precipitation during pluvial or interglacial periods. Responding to Quaternary climatic changes, hominin dispersal was channeled through vegetated corridors. This manuscript introduces a recently discovered group of Acheulean and Middle Stone Age sites far from the Nile Valley in the Eastern Desert (Sudan), referred to as Eastern Desert Atbara River (EDAR). The ∼5 m stratigraphy of the area is divided into three units (Units I–III) bounded by erosion surfaces. Each contains archaeological horizons. The EDAR area has rich surface sites with Acheulean horizons under the surface, singular finds of hand-axes within stratigraphic context in exposures, and large Acheulean sites partly exposed and destroyed by the gold mining activity. Optically stimulated luminescence (OSL) dating of Acheulean and MSA horizons from the EDAR 135 site indicates that the sedimentary deposits with stone artifacts were formed during the Middle Pleistocene between Marine Isotope Stages (MIS) 7 (pluvial) and 6 (interpluvial). Based on the OSL dating from the top of Unit IB, Acheulean artifact-bearing sedimentary deposits from overlying Unit IIA are younger than ca. 231 ka. Unit IA is the oldest Acheulean horizon in the EDAR area, not yet dated but definitively older than ca. 231 ka. An MSA horizon found in fluvial sediment was dated to be between 156 and 181 ka by OSL. The EDAR Pleistocene archaeological sites provide evidence for the presence of additional corridor(s) across Nubia, which connects the early hominin dispersals from the Nile and Atbara River systems to the Red Sea coast.

[link]

Midden or Molehill: The Role of Coastal Adaptations in Human Evolution and Dispersal

Manuel Will1,2,3 · Andrew W. Kandel4 · Nicholas J. Conard3,5
© Springer Science+Business Media, LLC, part of Springer Nature 2019

Abstract
Coastal adaptations have become an important topic in discussions about the evolution and dispersal of Homo sapiens. However, the actual distribution and potential relevance of coastal adaptations (broadly, the use of coastal resources and settlement along shorelines) in these processes remains debated, as is the claim that Neanderthals exhibited similar behaviors. To assess both questions, we performed a systematic review comparing coastal adaptations of H. sapiens during the African Middle Stone Age (MSA) with those of contemporaneous Neanderthals during the European Middle Paleolithic. In both species, systematic use of marine resources and coastal landscapes constitutes a consistent behavioral signature over ~ 100,000 years (MIS 6–3) in several regions of Africa and Europe. We found more similarities than differences between Neanderthals and modern humans, with remaining disparities all in degree rather than kind. H. sapiens exploited a wider range of marine resources— particularly shellfish—more intensively. MSA shellfish-bearing sites are also more often associated with intense occupations on coastal landscapes, and more evidence of complex material culture such as shell beads. In terms of broader ramifications, Pleistocene coastal adaptations are best conceived of as an ‘add-on’ to previous adaptive strategies, complementing more frequently exploited inland resources and landscapes. Still, Neanderthals and modern humans increased their dietary breadth and quality, and added options for occupation and range expansion along coastlines. Potential evolutionary implications of these multi-generational behaviors include higher intakes of brain-selective nutrients as a basis for neurobiological changes
connected to increased cognitive capacities, but also greater reproductive success, dispersal abilities and behavioral flexibility. Whether gradual differences between modern humans and Neanderthals stimulated different evolutionary trajectories is a question for future research. [pdf]

Keywords Paleolithic archaeology · Shellfish exploitation · Marine resources · Homo sapiens · Neanderthals

An evolutionary perspective on coastal adaptations by modern humans during the Middle Stone Age of Africa

Manuel Will, Andrew W Kandel, Katharine Kyriacou & Nicholas J Conard 2015
Quaternary International in press doi 10.1016/j.quaint.2015.10.021
http://dx.doi.org/10.1016/j.quaint.2015.10.021

The MSA of Africa documents the earliest & longest record of marine resource use & coastal settlements by Hs. Here, we provide a long-term & evolutionary perspective of these behaviors. We propose a definition of "coastal adaptations" rooted in the principles of evolutionary biology as a workable analytical device, we review the MSA archaeological record from Africa, to characterize the specific nature of coastal adaptations by Hs,
we evaluate current models, addressing the importance of coastal adaptations for human evolution, and we formulate new hypotheses within the larger framework of evolutionary causality by linking these behaviors directly to reproductive success.

The current archaeological record suggests that Hs occasionally consumed marine resources during the late-Mid-Pleistocene, but systematic & optimized gathering of a variety of marine food items dates to MIS-5 & -4. Archaeo-zoological studies show that people exploited marine resources in
a methodical manner on the Atlantic, Indian & Mediterranean coasts of Africa during this time frame. Despite the similarities in coast-lines, mobile huntergatherers also integrated these variable coastal landscapes into their settlement strategies for >100 ka, as shown by evidence for stable, repeated& planned occupations. Elements of complex material culture (bone tools, shell beads) occur particularly often in (near)coastal MSA sites.

The specific nature of coastal adaptations by Hs can thus be characterized by their systematic nature, long duration & verifiable impact on the
overall adaptive suite. By combining archaeological data with ethnographic, nutritional & medical studies, we propose several evolutionary scenarios for how Hs could have increased survival & fecundity rates by their specific adaptations to coastal environments. To test these hypothetical scenarios for the selective advantages of coastal adaptations for Hs, we need more data deriving from an expanded spatio-temporal archaeological
record, more formal evolutionary models & research strategies.

Isotopic evidence for initial coastal colonization and subsequent diversification in the human occupation of Wallacea

Patrick Roberts, Julien Louys, Jana Zech, Ceri Shipton, Shimona Kealy, Sofia Samper Carro, Stuart Hawkins, Clara Boulanger, Sara Marzo, Bianca Fiedler, Nicole Boivin, Mahirta, Ken Aplin, Sue O'Connor 2020 https://rdcu.be/b3Rwe 2020 Nature Communications open access

The resource-poor isolated islands of Wallacea have been considered a major adaptive obstacle for hominins expanding into Australasia.
Archaeological evidence has hinted that coastal adaptations in H.sapiens enabled rapid island dispersal & settlement, but there has been no means to directly test this proposition.

Here, we apply stable C & O isotope analysis to human & faunal tooth enamel from 6 Late-Pleistocene to Holocene archaeological sites across Wallacea:
the earliest human forager found in the region c 42 ka made significant use of coastal resources, prior to subsequent niche diversification shown for later individuals.
We argue that our data provides clear insights into the huge adaptive flexibility of our species, incl. its ability to specialize in the use of varied environments, particularly in comparison to other hominin spp known from Island SE.Asia.

Direct evidence for Late Pleistocene human coastal colonization of isolated islands beyond Wallace's Line

High profile genetic, fossil & material culture discoveries are forcing scientists to contend with an ever-more complex picture of interactions between different hominin populations during Late Pleistocene 126-12 ka. It has been hypothesized that what makes H.sapiens truly unique is its ability to rapidly colonize extreme environments during this time. Stable isotope evidence from fossil human teeth from isolated islands beyond the Wallace Line provide a detailed look at how H.sapiens adapted to challenging tropical circumstances over a 40-ky period.

Over the last 2 decades, archaeological evidence from deserts, high-altitude settings, tropical rain-forests & maritime habitats seem to increasingly show that Late Pleistocene human populations rapidly adapted to a nr of extreme environments (Roberts & Stewart 2018). By contrast, H.erectus & Neanderthals apparently used various mixtures of forests & grasslands. These broader ecological preferences may have made these other hominin spp vulnerable to drastic climatic changes (Rizal cs 2020), although finds of another hominin, Denisovans, on the Tibetan Plateau (Chen cs 2020) may indicate they were more flexible than previously assumed.

5 of us (CS, JL, SK, M, S O'C) have turned to the islands beyond Wallace's Line, to explore this question (over a decade of joint work between Austr.Nat.Univ & Universitas Gadjah Mada Indonesia). These islands were never connected to large neighbouring landmasses (even as falling sea-levels created larger land-masses of Sunda or Sahul), necessitating water-crossings if hominins were to reach them (Fig.1). Their interior environments have been considered resource-poor, covered in tropical forests that have often been seen as "barriers" to some of the earliest movements of H.sapiens (Curry 2016). Our joint excavations at a nr of key sites (e.g. Asitau Kuru, formerly Jerimalai) have shown that some of the earliest sapiens populations, to arrive in this part of the world ~45 ka, specialized in sea-faring & the use of marine resources, allowing them to rapidly colonize & move through these island systems. This has been demonstrated by the presence of archaeological fish-bones (e.g. tuna) & beautiful fish-hooks crafted from shells (O'Connor cs 2011). But the overall reliance of these humans on marine resources & the degree to which they ignored useful tropical plants & animals on shore have remained hotly debated (Anderson 2013).

Stable C isotope analysis of hominin fossil tooth enamel has been used for a long time in Africa to study the diets & environments of some of our earliest ancestors. Different types of resources (e.g. dense tropical forests vs grasslands vs the ocean) have different stable C*values. These differences are tracked into the tissues of animals that eat them: by studying the values of well-preserved human teeth, and comparing those to land & sea animals preserved at the same archaeological sites, we can get a better understanding of the overall reliance of an individual on these different food sources during teeth-formation.

Studying human teeth from the sites of Asitau Kuru, Lene Hara, Matja Kuru 1 & 2, Makpan & Tron Bon Lei on the islands of Timor & Alor, we were able to study the diets of humans from between 42 ka & the Neolithic. We can directly show that the earliest human fossil existing in Wallacea (c 42 to 39 ka) mainly relied upon coastal resources, but from 20 ka, humans began to consume inland tropical forest resources, likely incl. giant rats & carbohydrate-rich tropical plants that have recently been shown to be important parts of the diets of later farmers expanding through the region (e.g. Tromp cs 2020).

Our isotopic evidence supports recent human colonization models of Wallacea & Australia that suggest a rapid initial coastal colonization, followed by later inland settlement as populations expanded (Kealy cs 2017, Norman cs 2017), but our data also shows:

as populations expanded & social connections intensified later on in the Pleistocene, human populations began to make the interiors of these islands their homes as well. As a result, this Wallacean example shows different individuals & populations specialize in different ecological adaptations as time progresses, highlighting the overall flexibility of our species.

This data agrees with growing evidence that Late-Pleistocene human populations were able to rapidly come to terms with even the most extreme of environments, incl. deserts, high altitude settings, the palaeo-arctic & even tropical rain-forests. Other hominins (e.g. H.floresiensis) made water-crossings to reach past the Wallace line from 1 Ma, but the current ecological evidence associated with their fossils & occupation sites suggest that they made use of expanding grasslands, and associated medium to large mammals, that appeared in the region as a result of climate change (e.g. Brumm cs 2016, Roberts & Amano 2019). This fits with evidence for other members of the genus Homo elsewhere (incl.Neanderthals) that seem to have preferred a broader use of, albeit variable, mixtures of woodland & grassland habitats. In SE.Asia, it seems that extreme environmental changes & the Late-Pleistocene expansion of tropical rain-forest across the region may even have contributed to the eventual extinction of H.erectus (Rizal cs 2020) & perhaps other hominins, leaving H.sapiens as the last hominin standing by the end of the Pleistocene.

Future findings may challenge this view (applying the same methodology we show here to other hominins in SE.Asia would represent a fascinating comparison), but the current balance of evidence suggests H.sapiens was uniquely able to flexibly adapt to the variety of environments the Late-Pleistocene world's continents had to offer. This distinctive flexibility (supported by unique capacities of innovation, technological sophistication & social communication?) enabled H.sapiens to thrive in a variety of environments, and ride out increasingly extreme climate changes, even as certain groups may have locally failed.

Anderson A 2013 The antiquity of sustained offshore fishing. Antiquity 87:879-895 Brumm A cs 2016 Age and context of the oldest known hominin fossils from Flores. Nature 534:249-253 Chen F cs 2019 A late Middle Pleistocene Denisovan mandible from the Tibetan Plateau. Nature 569:409-412 Curry A 2016 "Green hell" has long been home for humans. Science 354:268-9 Kealy S, Louys J & O'Connor S 2017 Reconstructing palaeogeography and inter-island visibility in the Wallacean Archipelago during the likely period of Sahul Colonization, 65–45 000 Years Ago. Archaeol Prospect 24:259-272 Norman K cs 2017 An early colonization pathway into northwest Australia 70-60,000 years ago. Quat Sci Rev 180:229-239 O'Connor S, Ono R & Clarkson C 2011 Pelagic fishing at 42,000 years before the present and the maritime skills of modern humans. Science 334:1117-21 Rizal Y cs 2020 Last appearance of Homo erectus at Ngandong, Java, 117,000-108,000 years ago. Nature 577:381-5 Roberts P & Amano N 2019 Plastic pioneers: Hominin biogeography east of the Movius Line during the Late Pleistocene. Archaeol Res Asia 17:181-192 Roberts P & Stewart BA 2018 Defining the "generalist-specialist" niche for Pleistocene Homo sapiens. Nat Hum Behav 2: 542-550 Tromp M cs 2020 Exploitation and utilization of tropical rainforests indicated in dental calculus of ancient Oceanic Lapita culture colonists. Nat Hum Behav doi 10.1038/s41562-019-0808-y

New Evidence Shows That Humans Could Have Migrated to the Americas Along the Coast

Dating of rocks and animal bones shows Alaska’s coast was glacier free around 17,000 years ago, allowing people to move south along the coast. [Link]

Seafood helped prehistoric people migrate out of Africa, study reveals

Prehistoric pioneers could have relied on shellfish to sustain them as they followed migratory routes out of Africa during times of drought, a new study suggests.
The study examined fossil reefs near to the now-submerged Red Sea shorelines that marked prehistoric migratory routes from Africa to Arabia.
The findings suggest this coast offered the resources necessary to act as a gateway out of Africa during periods of little rainfall when other food sources were scarce.

The research team focused on the remains of 15,000 shells dating back 5000 years to an arid period in the region.
With the coastline of original migratory routes submerged by sea-level rise after the last Ice Age, the shells came from the nearby Farasan Islands in Saudi Arabia.

The researchers found that populations of marine mollusks were plentiful enough to allow continuous harvests without any major ecological impacts and their plentiful availability would have enabled people to live through times of drought.

Lead author Niklas Hausmann:
"The availability of food resources plays an important role in understanding the feasibility of past human migrations, hunter-gatherer migrations would have required local food sources, and periods of aridity could therefore have restricted these movements.
Our study suggests that Red Sea shorelines had the resources necessary to provide a passage for prehistoric people."

The study also confirms that communities settled on the shorelines of the Red Sea could have relied on shellfish as a sustainable food resource all year round:
"Our data shows that at a time when many other resources on land were scarce, people could rely on their locally available shellfish.
Previous studies have shown that people of the southern Red Sea ate shellfish year-round & over periods of thousands of years.
We now also know that this resource was not depleted by them, but shellfish continued to maintain a healthy population."

The shellfish spp found in the archaeological sites on the Farasan Islands were also found in abundance in fossil reefs dating to > 100 ka:
these shellfish have been an available resource over longer periods than archeological sites previously suggested.

Co-author Matthew Meredith-Williams:
"We know that modeling past climates to learn about food resources is extremely helpful, but we need to differentiate between what is happening on land & what is happening in the water.
In our study, we show that marine foods were abundant & resilient & being gathered by people when they couldn't rely on terrestrial food."