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Homo Sapiens and Neanderthals: Encounters of the Close and Personal Kind

Josie RMills29 January 2019

The two most common questions I get asked about Neanderthals are ‘Why did they go extinct?’ and ‘Did we have sex with them?’ (although never phrased that directly). Neanderthals first appeared in the fossil record around 430 thousand years ago (kya) and persisted through the Mid to Late Ice Age until disappearing approximately 40 kya. They evolved outside of Africa, from existing hominin (human like) populations that had migrated there before 400 kya, and lived in Europe, the Middle East and Western Eurasia. H. neanderthalensis is very closely related to H. sapiens, who are our direct ancestors, with genetic evidence suggesting that we shared a last common ancestor until around 750–550 kya. Although this sounds like a long time ago, the earliest stone tools made by a human ancestor are around 3 million years old.

The publication of the first complete Neanderthal genome in 2010 revealed that all non-African modern humans retain approximately 2% Neanderthal DNA, indicating interbreeding between the two species. So, yes, humans did have sex with Neanderthals, probably about 60–80 kya when they left Africa and encountered established Neanderthal populations in the Middle East. But before this grosses you out, remember that most reconstructions of Neanderthals pre-2010 and particularly during the 19th century were heavily loaded with an ‘us and them’ mentality. Basically, the more ape-like the portrayal of Neanderthals, the more elite and unique humans appear. We know that this is not the case now, with a myriad of new discoveries linking Neanderthals to cultural and symbolic practices, and advanced anatomical adaptations. There is no evidence to suggest the two species would not have recognised each other as what we would call ‘humans’.

A H. neaderthalensis (right) and H. sapien (left) skulls, facing each other. Image credit: hairymuseummatt (original photo), DrMikeBaxter (derivative work) [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

 

As more Neanderthal genomes are studied scientists are analysing why we have retained these pieces of DNA. The initial contribution of Neanderthal DNA was likely higher at around 6% but as humans have evolved some genes were selected out. Studies  suggest that the genes we retain are related mainly to phenotypic qualities, meaning those that affect our outward appearance, for example hair and skin colour. Researchers at the Max Planck institute proposed that these genes are all linked to climate adaptation and sunlight exposure, demonstrating characteristics linked to the Neanderthal’s c. 400 kya stay in cooler climates (Dannemann and Kelso 2017).

But Anatomically Modern Humans may have inherited something much more practical from Neanderthals in the form of a genetic resistance to some viruses. Researchers have proposed that when H. sapiens left Africa they encountered viruses that their bodies were not adapted to fight. Historically we know that these kind of encounters can be fatal, think the smallpox epidemics brought by the Spanish to Mexico leading to the downfall of the Aztec civilisation. Enard and Petrov (2018) propose that by breeding with Neanderthals, who had been exposed to these pathogens for around half a million years, H. sapiens became immune and were able to survive in Europe and beyond.

In archaeology and palaeoanthropology, the traditional model of linear evolution and direct replacement of species is becoming more and more difficult to uphold, with discoveries like the Denisovans and others living during similar time spans. At this point you might could say at times the Ice Age was a bit more like Middle Earth! There is a growing openness, supported by scientific evidence, to accept more nuanced views of interaction between different human species.

References:

Dannemann, M., & Kelso, J. (2017). The contribution of Neanderthals to phenotypic variation in modern humans. The American Journal of Human Genetics, 101(4), 578-589.

Enard, D. and Petrov, D.A., 2018. Evidence that RNA viruses drove adaptive introgression between Neanderthals and modern humans. Cell, 175(2), pp.360-371.

Green, R.E., Krause, J., Briggs, A.W., Maricic, T., Stenzel, U., Kircher, M., Patterson, N., Li, H., Zhai, W., Fritz, M.H.Y. and Hansen, N.F., 2010. A draft sequence of the Neandertal genome. science, 328(5979), pp.710-722.

Slon, V., Mafessoni, F., Vernot, B., de Filippo, C., Grote, S., Viola, B., Hajdinjak, M., Peyrégne, S., Nagel, S., Brown, S. and Douka, K., 2018. The genome of the offspring of a Neanderthal mother and a Denisovan father. Nature, 561(7721), p.113.

Wolf, A.B. and Akey, J.M., 2018. Outstanding questions in the study of archaic hominin admixture. PLoS genetics, 14(5), p.e1007349.

 

 

 

 

 

 

 

Foreign Bodies: Attack of the Clones

GemmaAngel18 February 2013

Profile  by Felicity Winkley

 

 

 

 

 

One of the most controversial specimens amongst the Grant Museum’s encyclopaedic collection is a preserved domestic cat; in fact, on one occasion, I was standing quite close to this object at the exact moment when a small child laid eyes upon it and promptly burst into tears. The fact that the sight of preserved animals, particularly domesticated or fluffy ones, provokes such a response would be ample topic for a debate in its own right, however in this instance I am more interested in the way the Grant have developed the subject in their museum signage. Beside the exhibit, they point out that in 2004 the first domesticated cat was cloned for $50,000 – a kitten called ‘Little Nicky’, commissioned by a Texan woman called Julie after the original cat ‘Nicky’ had died [1] – and ask whether or not this was a good thing to do? nickyAt the time of the cloning in 2004, the response from the scientific community was negative: it was thought a fatuous use of the technology to reproduce a domestic pet, as well as inhumane given the animal’s short life-expectancy (roughly a third of cloned cats did not survive beyond 60 days).[2] Today, expanding the subject beyond the cloning of domestic animals, as part of the successful QRator scheme (in which visitors are invited to record their responses to topical questions relating to the collections), the Grant Museum asks the public to contribute to a wider debate: Should we clone extinct animals?

The argument is a complex one. For one thing, extinct animals may have died out because of their own comparative weaknesses, and therefore any attempts to reintroduce them may prove futile. The journalist Chris Packham, for example, has famously lambasted attempts to conserve the Giant Panda, criticising the huge amounts of money spent on attempting to breed an animal which is so reluctant to reproduce itself. He suggests that the Giant Panda is “a species that of its own accord has gone down an evolutionary cul-de-sac” and therefore should be allowed to die out, not least because any attempts to reintroduce it into the wild will be limited by the increasingly diminishing area of its potential habitat anyway.[3] Where cloning animals and reintroducing them is concerned, habitat is also an issue in terms of preempting any potential environmental changes that might have occurred since the species was last present in the wild. The repercussions of reintroducing clones despite drastic ecosystem change are fairly clearly (if not necessarily realistically!) laid out for us to see in Jurassic Park. Although the author accepts this is an extreme example, it is nevertheless an effective visualisation of what can occur when we tamper with complicated systems of which we have limited understanding.

Jurassic Park III

 

But what of those species made extinct by human influence, and through no fault of their own? The quagga, hunted to extinction in 1883, and the thylacine, in 1936, are both on display in exhibition cases at the Grant Museum. If we accept, then, the fault of human oversight, perhaps these two could justifiably be cloned and reintroduced into the wild – but given the cost of the procedure and the potentially limited life-span of the animal subjects, wouldn’t the enormous investment be better applied to conserving those species still alive today but in dire need of assistance? The Amur leopard population, for example, is currently at a critical low, with just 7-12 thought to remain in the wild in China and 20-25 in Russia.[4]

Taking into account all of these conflicting arguments where cloning is concerned, it was with some interest, therefore, that I read a few weeks ago about a Harvard professor’s hopes for recruiting a female volunteer willing to surrogate a baby created with Neanderthal DNA.[5] Geneticist Professor George Church has recently completed enough Neanderthal bone-sample analysis to accurately isolate the genetic code that would enable him to create artificial Neanderthal DNA, according to his publication Regenesis: How Synthetic Biology Will Reinvent Nature and Ourselves.[6] Having previously been involved in the Human Genome Project, which successfully mapped human DNA, Professor Church would insert artificial Neanderthal DNA into stem cells and inject these into a human embryo in the earliest stages, allowing this to develop in the laboratory before implanting it into the womb of a potential surrogate mother. He believes that Neanderthals, whose population flourished in Europe and extended throughout the Middle East and into China between 70,000 and 30,000 years ago, were highly intelligent. This impression is certainly supported by archaeological evidence: the skulls of Neanderthals held large brains, “in the range of and exceeding the cranial capacity of modern humans” state Lewin and Foley.[7] As such, Professor Church proposes that a cloning and reintroduction of Neanderthals could be useful to increase diversity, and introduce an alternative way of thinking into society:

When the time comes to deal with an epidemic or getting off the planet or whatever, it’s conceivable that their way of thinking could be beneficial. They could maybe even create a new neo-Neanderthal culture and become a political force. The main goal is to increase diversity. The one thing that is bad for society is low diversity.[8]

Aside from the obvious concerns about the potential risks to the surrogate mother of a baby created via this method, critics have also challenged the ethics of the proposed experiment. Whilst the Charter of Fundamental Rights of the European Union prohibits reproductive human cloning in member states of the EU, and it is likewise illegal in the UK under the Human Fertilisation and Embryology Act 2008 – because the project proposes the cloning of a Neanderthal rather than a Homo Sapiens, there are fears that current legislation may not apply. In any case, there is no uniform guideline agreed for the United States of America on human cloning, whether reproductive or therapeutic. But were Professor Church to have his way, how would a new Neanderthal cope in modern-day society? Physically, could their immune system withstand it? Emotionally, would they successfully integrate, or be outcast as a monster? Whatever the answer – and luckily at the moment our concerns are purely speculative – there is no denying that a neo-Neanderthal person would be the ultimate foreign body.