San (Khoisan) and Europeans

Following my previous post on similarities between San people in southern South Africa, and Europeans, I read a paper about the San (Khoisan) and their "antiquity". It reports them as an ancient population that retained a large effective population while that of other groups fell (i.e. other Africans, Europeans, Asians, and the Out of Africa migrants).

The paper published in Nature in 2014 by Kim et al., (Khoisan hunter-gatherers have been the largest population throughout most of modern-human demographic history). The image below shows how Ne (effective population) evolves over time (oldest to the right), for San, African Yoruba, Europeans, and Asians. As you can see all groups (actually, the ancestors leading to each of these populations) have similar population sizes till 100,000 years ago when a dramatic drop in population sizes occurs. I don't understand how they obtained Ne values for hominin populations 2 to 4 million years ago, this was the days of Australopiths and probably Homo habilis.

Effective population sizes for San, Africans, Asians and Europeans. Fig. 3 a in Kim et al., 2014

This drop in effective population size is attributed to climate changes within Africa. The paper includes a series of maps as Fig. 12 in its Supplementary Material to explain the process. They can be seen below:

Modern humans originated in Africa (a), blue circle in South Africa seems to imply an origin there, though the paper does not specify the location. Then these people spread north (b), the orange oval marks the new territories. Then came the climate change (c) around 150 or 100 kya. Drought in western and central Africa hit the humans there in central, western, and eastern Africa, but spared the San people in the southern part of Africa. This coincided with a fragmented population (structured) with isolated groups that did not interact with each other (see the different dots and colors on the map, marking these groups). Populations declined central and western Africa, and when the ancestors of Non-Africans (green arrows) (d) migrated Out of Africa (OOA), they carried this lower Ne, and it dwindled even more due to bottlenecks and founder effects as they advanced into Eurasia. The San, however, kept their population intact.

The authors reconstruction of this period is summarized as follows: "After the earliest split, between the ancestral Khoisan and non-Khoisan populations ~100–150 kyr ago, the ancestral Khoisan population maintained their high genetic diversity, while the effective population size of the non-Khoisan continued to decline for 30~120 kyr ago and lost more than half of its diversity. The ‘Out of Africa’ migration ~40–60 kyr ago accounts for the observed population split between African and non-African populations, and the subsequent smaller effective population size of non-Africans compared with non-Khoisan Africans."

Comments

However, and interestingly, as pointed out in my previous post, the San and Europeans share several unique allele variants that are ancestral (found also in Neanderthals and Denisovans) whcih confer lighter pigmented skin than that found among the remaining Africans and also South Asians and Australo-Melanesians, who carry a later (derived) mutation for darker pigmentation.

How does this similarity between a specific OOA group and San people tie in with the evolution and migration sproposed by Kim et al.?

Not well. We would have to imagine a group that split from the San, moved north, lived in isolation in Central Africa, then survived the climate crisis there, moved north, left Africa, surviving the founder effect, bottlenecks and genetic drift, established themselves in Europe and somehow managed to keep their skin-color alleles intact. While all the other groups in Africa mutated and adopted a dark skin set of alleles. Too complex to be the explanation.

The San (Khoisan or bushmen) have always intrigued me since the 1980s movie "The Gods Must Be Crazy", I was taken aback by their pale skin and oriental factions. So different from the usual African features. People living in the deserts of Namibia with a hunter-gatherer culture in the 20th century! I have never found a paper explaining their similarity with East Asians. I will explore this strange trait in a coming post.

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Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2026 by Austin Whittall © 

South African musings

Cape Agulhas, southernmost tip of Africa. Photo by Austin Whittall May 2012.
Copyright © 2012 by Austin Whittall

I visited South Africa. During the last two weeks my wife and I have taken a lovely vacation to that great country at the tip of the African continent. This is not the place to go into its turist attractions, the beauty of its landscape, the friendliness of its people, its wildlife, great food and wines, so please be assured that I won't bore you with my travel anecdotes. Instead I will post some thoughts on the peopling of South America starting out from the African Continent.

The nasty waters south of Africa

I had the opportunity to see the rough South Atlantic Ocean beating upon the rocky shores of the Cape of Good Hope, Hermanus and Cape Agulhas. I also experienced the Indian Ocean's surf roaring against beaches and cliffs along the south of South Africa between Port Elizabeth and Cape Agulhas. The sea is really rough.

The sight of these choppy waters has has made me reconsider the theory that I have mentioned in previous posts (The South African Out of Africa), which suggests that our ancient ancestor Homo erectus crossed these waters and skirted the Antarctic continent to reach America.

No man (or hominin) in his senses would dare venture into those roaring waves.

The photograph above was taken at the southernmost point of Africa, Cape Agulhas (34° 49' 58"S, 20° 00' 12"E), where the Indian Ocean and Atlantic Ocean waters meet.

Ancient record of humans in Southern Africa

I also had the chance to visit a caveat Mossel Bay, on the point, under the lighthouse.

Located at 22° 10' E and 34° 12' S the Cape of St. Blaize separates the rough Indian Ocean waters from those of Mossel Bay. The tip of the Cape was named after the Saint of the day Portuguese navigator Bartolomeu Dias spotted this part of the world, in February 1488. He named the place Aguada de Sao Bras (Watering place of St Blaize).

The cave is actually an overhang, is known as Bat Cave and is set on Cape St. Blaize. It was excavated partially by Leith in 1888 and again in 1932 by A. J. H. Goodwin and B. D. Malan, who reported their findings in 1935. [1] The stone tools were described as Middle Stone Age "Mossel Bay Industry" and record about 165,000 years of human presence in this area.

The cave itself is about 30 m (95 ft) above sea level and is about 90 ft wide by 40 ft deep (27 by 12 m). It faces towards the southeast and offers a lovely view of the surf below. The following photograph shows both cave under the lighthouse:

Bat Cave at Mossel Bay. Photo Austin Whittall Copyright © 2012 by Austin Whittall

So, modern humans have lived here for most of our existence as a distinct group of hominins. On the flight back to Buenos Aires, I read an interesting article [2] that made me wonder if other more ancient groups such as Australopithecus sediba may have lived at Mossel Bay or roamed the coasts of Southern Africa.

A. sediba may be the link between our homo genus and the more distant and primitive Australopithecines and has been proposed as an ancestor to H. erectus . These hominins lived about 2.3 Mya and their remains have been found at Johannesburg.

Could they be the ones that made it to Georgia? Was it they who left Africa before H. erectus? Since I am now discarding the South Atlantic route, could they have drifted across the more benign Equatorial route pushed by ocean currents? (see my post on the Trans Atlantic route) Or did they trek all the way into America across Asia and Beringia?

Further reading

[1] A. J. H. Goodwin and B. D. Malan, Archaeology of the Cape St. Blaize Cave and Raised Beach, Mossel Bay. Annals of the South African Museum, Vol. 24, part 3, S. 111-140

[2] Kate Wong, First of Our Kind: Could Australopithecus sediba Be Our Long Lost Ancestor?. Sensational fossils from South Africa spark debate over how we came to be human. Scientific American. March 20, 2012.

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Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2012 by Austin Whittall © 

The South African "out of Africa" route

My last posts have dealt with a Brazilian geologist and Archaeologist, Maria Beltrão. She has proposed that our distant relative, the H. erectus reached America over 1 million years ago. Below I post about her and the route she proposes for this migration of H. erectus into America.

Beltrão writes about herself

Beltrão points out in an article [1] that hominids have been living in Asia at least since 1.8 million years ago (in Indonesia, central China and Pakistan), and also in Georgia, (the remains are probably anHomo habilis), with this in mind, she adds:

“If over 5 million years ago, animals crossed from Asia to America and vice versa, man, being a hunter why did he say “no” to America and did not follow his prey during the last 2 or 4 million years?”[1]

As a geologist, she has sought out sites whose surface is sealed off, either with marl as at Toca da Esperança, or with lava as at Itaboraí, to ensure undisturbed layers.

The South African gateway

She proposed (together with Paepe, 1978 - I have not been able to find the paper / article) a migration from South Africa to South America during the glacial period, crossing the ice pack.

This is an interesting “Out of Africa” route, it must go south, cross the sea between South Africa and the ice pack surrounding the Antarctic, then go along the pack’s coastline till it reaches America and from there, back up, into Patagonia. A long and risky journey that combines sailing and trekking along the ice pack.

I have posted about a possible route via the Antarctic into South America, but from the West, from Australia, New Zealand and Tasmania. An equally difficult and longer route than the South African one.

To get an idea of what would have to be trekked – sailed – navigated, I combined two different maps that depict the coastline of Southern Africa and the Southern part of South America during the Last Glacial Maximum (LGM), when most of the water was stashed away in the form of gigantic ice sheets covering the Northern Hemisphere, Antarctica and parts of South America and New Zealand. The sea level dropped and exposed parts of the continental shelves of both continents (shaded in light green). The sources of the maps are [2] and [3]. I also added another map taken from[4], and adapted from its FIG. 5. Which shows the ice thickness in meters (filled color contours) winter during the LGM. South Africa not included in the original map, was added by me. The red arrow shows the possible land and sea route that could be used to reach America from Africa.

I am well aware that our friend, the H. erectus would have reached America long before the last Ice Age and its LGM, yet even so, I chose the LGM coastline for two reasons: one, that all previous glaciations would have provoked a similar drop in sea level and, two, that I could not find any data on previous glaciation coastlines.

Below are the maps:

Maps showing Antarctic route from South Africa to America. LGM coastline given as a reference. Adapted by A. Whittall from [2][3] and [4]

I believe that the circumpolar current flows from West to East and therefore would hinder a direct navigation across the South Atlantic. But I must check to see if this is valid for glacial periods.

Sources

[1] Maria Beltrão, (2008). Depoimentos de Arqueólogos pioneiros: Maria Beltrão, ISSN 1807-1783, atualizado em 02 de abril de 2008. História e-História

[2] C.Leigh Broadhursta et al, (2002). Brain-specific lipids from marine, lacustrine, or terrestrial food resources: potential impact on early African Homo sapiens . Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology. Volume 131, Issue 4, April 2002, Pages 653–673

[3] L. Miotti and M.C. Salemme, (2003), When Patagonia was colonized: people mobility at high latitudes during Pleistocene/Holocene transition. Quaternary International. Volumes 109–110, 2003, Pages 95–111

[4] Otto-Bliesner, et al, (2006). Last Glacial Maximum and Holocene Climate in CCSM3 J. Climate, 19, 2526–2544. doi: http://dx.doi.org/10.1175/JCLI3748.1

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Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2012 by Austin Whittall ©