Do modern humans descend from Neanderthal?
Neanderthal has long suffered from a bad image and continues to evoke a series of misconceptions.
Soon after the first skeletons were discovered in Belgium (1829), Gibraltar (1848) and Germany (1856), scientists of the time claimed that the Homo neanderthalensis, as it had been named, was not human. They imagined that it was some sort of beast-like primate, closer to the gorilla or the Yeti than to modern humans. We now know that these early inhabitants of Europe, not found on other continents apart from the Near East and Central Asia, actually looked much more like us than anything else. Here is a reconstruction of a Neanderthal child from Gibraltar by the Anthropological Institute, University of Zürich.
The most deeply rooted misconception, still widespread in the scientific world, is that Neanderthal became extinct, without leaving any contribution to modern humans. Morphological comparison between Neanderthals and modern Europeans immediately reveals striking similarities in unique physical traits not found among Africans (see below). The sequencing of the Neanderthal genome, completed in 2010, has definitely proven that, not only Europeans, but all non-African people today inherited a few percents of Neanderthalian DNA.
Were Neanderthals less evolved than Homo sapiens?
One first misconception is that all Neanderthals were the same. The proto-Neanderthals first appeared some 350,000 years ago, at a time when our Homo sapiens ancestors were still fairly primitive Homo erectus, with a brain size of 900 to 1100 cc.
Neanderthal roamed Europe until 30,000 to 24,000 years ago, when its presence progressively disappears from the archeological record. Naturally, there was plenty of time for evolution in over 300,000 years, and many sub-species developed (see Fabre 2009). It is likely that there was a greater genetic distance between the most different Neanderthals subspecies than between modern human ethnic groups.
When the Homo sapiens sapiens (also known as anatomically modern humans) arrived in Europe about 40,000 years ago, Neanderthal was at its most advanced level of evolution. Its cranium, with a volume ranging from 1200 to 1700 cc, was in fact larger than that of Cro-Magnons (Paleolithic European Homo sapiens), and also 10% greater than that of modern humans in average. If brain size is any indication, Neanderthals could have been cleverer than us. But that's not the whole story. Neanderthal's skull had a lower vaulted prefrontal cortex than most modern humans, and it has been speculated that they would have been worse at decision making and moderating social behaviour. On the other hand, Neanderthals possessed a bigger occipital lobe, meaning that their visual abilities (including the distinction of details and colours) were certainly better than that of modern humans.
Scientists have long looked down on Neanderthals, claiming that it wasn't evolved enough to speak or to use tools like the Homo sapiens. This has since been proven wrong by genetics. The very reputable Nature journal has published that Neanderthals were genetically equipped for language. Another study (D'Anastasio 2013) confirmed that Neanderthals could talk, based on the horseshoe-shaped structure in their neck.
Numerous studies have shown that Neanderthals and Cro-Magnons used similar tools, and overall had the same technology and lifestyle. Both buried their deads, with similar ornaments, demonstrating the same level of sentiments and care. Actually Neanderthals were the first hominids to practise interment, long before Homo sapiens existed. The oldest evidence of intentional Neanderthal burial dates back to 300,000 years before present at the Atapuerca Cave in Spain. Some 15 Neanderthal bodies found in Pontnewydd Cave in Wales show deliberate disposal of the dead some 225,000 years ago. Another famous example is the Krapina Cave in Croatia, where over 70 Neanderthals were found ceremonially buried with the help of tools some 130,000 years ago (source). The earliest evidence of religion also comes from Neanderthals, in the form of totemism or animal worship, such as bear cult.
A lot of people imagine Neanderthals as hunters whose diet was dominated by meat from big game. But they actually enjoyed a diversified diet than that, eating mussels and other shellfish (which were warmed up to open their shells), fish, grass seeds like wheat and barley (which were cooked), legumes, nuts, fruits, and even bitter-tasting medicinal plants such as chamomile and yarrow.
Stanley Finger explains in his book Origins of Neurscience that a 70,000-year old Neanderthal skull from the Shanidar Cave in Iraq showed evidence of healed skull wounds. So it is possible that Neanderthals had some knowledge of basic medicine before Homo sapiens even reached Europe.
João Zilhão et al. (2010) reported finding sculpted shells painted by Neanderthals 50,000 years ago in Iberia. Thhis was the first evidence that Neanderthals used jewellery, but also that they could manufacture paint. The discoverers think that Neanderthals would also have painted their bodies. It has been proposed that the world's oldest cave paintings, such as those of Cave of El Castillo in Cantabria and the Nerja Caves near Malaga in Spain dating from circa 40,000 years ago, were also the work of Neanderthals, or possibly of early Sapiens-Neanderthal hybrids (source). It is not surprising to find the origins of painting among Neanderthals considering that they had a larger occipital lobe than Homo sapiens, which would have made them more visual thinkers.
Neanderthals also preceded Homo sapiens in making string or rope, the oldest specimen of which having been found at a 90,000 year-old site in France (source), that is 60,000 years earlier than Homo sapiens, as far as we know.
What did Europeans inherit from Neanderthal?
All Eurasian people apparently inherited various Neanderthalian genes relating to the immune system (e.g. HLA types), including genes that increased the risk for some autoimmune diseases such as type-2 diabetes and Crohn's disease. Physical features inherited from Neanderthal by Europeans and Middle Easterners include prominent eyebrows, big eyes, strong jaws and wide shoulders. 70% of East Asians also inherited mutations in the POU2F3 gene, which is involved in keratin production and may be responsible for straightening hair.
According to the Canadian anthropologist Peter Frost, the current level of hair colour diversity in Europe would have taken 850,000 years to develop, while Homo sapiens has been in Europe no longer than 45,000 years. This is evidence enough that genes for fair hair were inherited from interbreeding with Neanderthals.
DNA tests demonstrated that Neanderthals possessed fair skin, and at least some subspecies had reddish hair too.
Homo sapiens apparently did not inherit the whole light skin, light eyes and light hair package at once, but through continuous interbreeding with various Neanderthal subspecies in Europe, the Middle East and Central over tens of thousands of years. It has been confirmed that Mesolithic Europeans had blue eyes, but dark skin and dark hair.
There are several genes influencing skin colour. Among them, the BNC2 gene, which influences saturation of skin colour and is responsible for freckling, was confirmed by Sankararaman et al. (2014) to have come from Neanderthal. It is found at varying frequencies in all Eurasian populations and is most common among Europeans (70% have at least one copy of the Neanderthalian version, against 40% for East and South Asians). Mutations in the SLC24A5 gene, responsible for 40% of skin colour variations between Europeans and sub-Saharan Africans, appear to have been spread to Europe by Neolithic farmers from the Near East and especially by the Proto-Indo-Europeans from the Pontic Steppe during the Bronze Age (more info). Mutations for blond and red hair have yet been not found in ancient European samples prior to the Bronze Age. So it seems that fair skin and blond or red hair were originally passed on to Homo sapiens in the Middle East or Central Asia, rather than in Europe.
As for the genes for light eyes, there is a relatively high likelihood that they were inherited from Neanderthals too, rather than having emerged independently in Europeans fairly recently. It hasn't been proven yet that Neanderthals had blue, green or hazel eyes because only one Neanderthal sample has been fully sequenced at present. But the statistical probability that such mutations would arise and be positively selected in Neanderthals, who evolved for 300,000 years in the high latitudes of Europe, is far higher than in European Homo sapiens, who have lived for only 45,000 years in Europe, and less than 30,000 years in northern Europe. Not all Neanderthal groups would have been blue eyed, though. Neanderthals were much more genetically diverse than modern humans, who all share a recent ancestry three times earlier in time than Neanderthals subspecies between themselves. If blue eyes indeed originated in Neanderthal, different Neanderthal populations could have passed blue eyes genes several times to Homo sapiens in Europe, the Middle East or Central Asia. It's not even granted that the two main genes, OCA2 and HERC2, were passed at the same time or to the same people. They might only have converged later in Europeans. Another alternative is that only one of these genes came from Neanderthal while the other arose in Homo sapiens.
Mesolithic Europeans from Spain and Luxembourg have been confirmed to have possessed the HERC2 mutation for blue eyes (see Olade et al. (2014) and Lazaridis et al. (2014)). This mutation is also found in parts of Asia settled by the Proto-Indo-European speakers belonging to the paternal lineages R1a and R1b, including the Altai, southern Siberia, Central Asia, Iran and the Indian subcontinent. Since the the Proto-Indo-Europeans carried very different paternal lineages from Mesolithic Europeans (Y-haplogroups C, F and I), and only shared a few very old maternal lineages, like haplogroups U4 and U5, their HERC2 mutation could have been inherited from a common Paleolithic ancestor or passed on by two different groups of Neanderthals to separate Upper Paleolithic Homo sapiens.
Physical traits of Neanderthals inherited by modern Europeans
All non-Africans today may have a roughly equal proportion of Neanderthal DNA, but some of the most visible physical traits appear to have been inherited especially by modern Europeans, and northern Europeans in particular. Here is a list of traits that distinguished Neanderthals from Homo sapiens, but that you could also have inherited if you are of European or Western Eurasian descent.
- Occipital bun : a protuberance of the occipital bone (back of the head) that looks like a hair knot. You have it if you can feel a rounded bone just above the back of your neck (same height as the ears).
- Low, flat, elongated skull : What matters here is especially the 'elongated skull', as opposed to the back of the skull falling almost vertically, like all East Asians, and most Anatolian, Caucasians and Eastern Europeans. Elongated skull are particularly common in Scandinavia, in the British Isles and in Iberia.
- Retromolar space posterior to the third molar: i.e. an empty space behind the "wisdom teeth".
- Supraorbital torus : protruding eyebrow bone (including big deep eye cavity between the eye and eyebrow).
- Bigger, rounder eyes than average.
- Broad, projecting nose : angle of the nose bone going more upward than average (not falling straight like a "Greek nose").
- Bony projections on the sides of the nasal opening : i.e. nose bone making a "triangle" between the nose and cheeks/orbits.
- Little or no protruding chin
- Larger mental foramen in mandible for facial blood supply : this means that the side jaw and cheek are bigger or better supplied in blood than average. This increased blood supply could result in the cheeks being red (like blushing) when doing physical exercise or when the weather is cold.
- Short, bowed shoulder blades : i.e. shoulder bones curving toward the front more than average.
- Large round finger tips : typically "flat" and wide finger tips, especially the thumb (e.g. if your thumb is more than 1.5 cm wide).
- Rufosity : i.e. having red hair, or brown hair with red pigments, or natural freckles.
- Fair skin, hair and eyes : Neanderthals are believed to have had blue or green eyes, as well as fair skin and light hair. Having spent 300,000 years in northern latitudes, five times longer than Homo sapiens, it is only natural that Neanderthals should have developed these adaptive traits first.
How quickly did Homo sapiens replace Neanderthals?
The Sapiens-Neanderthal hybridisation was probably an extremely protracted process, in which a constant flow of Homo Sapiens from Africa and the Middle East progressively diluted Neanderthal DNA. The first migration of Homo sapiens into Europe could have started as early as 100,000 years ago, albeit in such small numbers that no archeological trace of it could be found to date. Regular H. sapiens migrations from the Near East or Northwest Africa (via the Strait of Gibraltar) would have continued throughout the Paleolithic, just as new waves of immigration occured during the Late Glacial period, the Mesolithic, the Neolithic and the Bronze Age.
There is undeniable skeletal evidence that Neanderthals evolved and became less robust and closer to Homo Sapiens over time, starting at least 100,000 years ago. Mediterranean Neanderthals were the ones that became less robust and showed the most signs of possible hybridisation, while their northern counterparts remained closer to older types of Neanderthals. If interbreeding with Homo sapiens did occur so early, it would have been in southern Europe first.
During the Middle Paleolithic (until 50,000 ybp), Homo sapiens presence in North Africa and Southwest Asia would have been too small for migrations to have a serious genetic impact on Neanderthalian populations in Europe. But as the H. sapiens population grew during the Upper Paleolithic, their genes began to outnumber those of Neanderthals in Southeast Europe, then little by little over the rest of Europe. If regular interbreeding took place, Neanderthalian traits eventually got so diluted that they seem to disappear from the archaeological record roughly 25,000 years ago.
There is even evidence that Neanderthals could have survived well into modern times. For example, the Almas, a cryptozoological species of presumed hominid, is reputed to inhabit the Caucasus and Pamir Mountains of Central Asia. Almas are typically described as human-like bipedal animals, between 150 and 200 cm (5 to 6.5 ft) tall, their bodies covered with reddish-brown hair, with anthropomorphic facial features including a pronounced browridge, flat nose, and a weak chin. Many cryptozoologist researchers have been struck by the similarity between these descriptions and modern reconstructions of how Neanderthals might have appeared. One such hominid was captured in the wild in Abkhazia, Western Caucasus (now in Georgia) in the late 1800's. Her name was Zana (read more).
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