Neanderthals more ‘human’ than once thought

Sébastien Chabal, the gigantic and hairy back-row forward in the 2007 French World Cup rugby team, was nicknamed ‘The Caveman’ by French fans. Indeed he is an awesome spectacle, at almost 2 m tall and weighing over a tenth of a tonne, with great black beard and locks. But is seems that Neanderthals were redheads and probably prone to sunburn (Lalueza-Fox, C. and 16 others. 2007. A melanocortin 1 receptor allele suggests varying pigmentation among Neanderthals. Science, v.  318, p, 1453-1455). The team analysed DNA extracted from Neanderthal bones from Spain and Italy, and identified the mc1r gene that regulates pigmentation in many mammals. In both specimens it turned out to be a variant that is associated with fair skin and red hair. An artist has rendered a French Neanderthal man’s physiognomy from his skull, by combining this information with modern facial reconstruction techniques (in Culotta, E. 2007. Ancient DNA reveals Neandertals with red hair, fair complexions. Science, v. 318, p. 546-547). He seems set to become a pin-up among those ladies who favour the larger gentleman, even having a nose far larger than that of Gerard Depardieu. Although proof of the growing power of genetic analysis of ancient tissue, that Neanderthals were probably pale-skinned is not really surprising. They inhabited high latitudes for at least 200 ka longer than modern Europeans have, and the pale variant of mc1r is advantageous where sunlight is at a premium for creating vitamin D. Like modern Europeans, their immediate ancestors who migrated northwards were almost certainly dark-skinned.

Yet by far the most scientifically exciting outcome of the team’s work is the extraction from the Spanish Neanderthal bones of the FOXP2 gene, which is implicated in the development of speech and language (Krause, J. and 12 others 2007. The derived FOXP2 variant of modern humans was shared with Neandertals. Current Biology, v. 17, p. 1908-1912). It shares two mutations with FOXP2 in modern humans, that had previously been suggested only to have developed in the last 100 ka, so must have been present in the last common ancestor of fully modern humans and Neanderthals, around 300 to 400 ka. Although this discovery cannot prove that Neanderthals spoke, taken along with emerging evidence that symbolic skills were used by even earlier hominins (see When and where ‘culture’ began in November 2007 issue of EPN) it does suggest they were capable of as much sophistication as the earliest fully modern humans.

Is human evolution speeding up?

Another outcome of the acceleration in genetic analysis is an ability to scan vast numbers of differences in DNA from many individuals.  Highly productive are single nucleotide polymorphisms or SNPs (‘snips’) that are available from the international HapMap project. From analysing almost 4 million SNPs from 270 individuals has emerged an intriguing parallel between human population explosion since about 40 ka and an increasing rate at which new genetic traits have been incorporated into the human genome (Hawks, J. et al. 2007. Recent acceleration of human adaptive evolution. Proceedings of the National Academy of Sciences, v. 104, p. 20753-20758). The link is not entirely surprising, for the exposure of more individuals to mutagenic factors will result in more mutations entering the total gene pool. Yet ‘weeding-out’ of unfavourable mutations also operates over time, so the fact that around 7 % of human genes seem to have changed over the last 40 ka, indicates the overall rate of human evolution must have speeded up remarkably. The analysis suggests that the rate rose to a peak between 5000 and 8000 years ago, for Europeans and West Africans respectively. ‘Received wisdom’ has for a long while been that fully modern humans went through a phenomenal spurt in evolution around 50 to 40 ka (but see When and where ‘culture’ began in November 2007 issue of EPN), and that somewhat Eurocentric view is overturned by the SNP evidence. Selection pressures must have risen to a peak around the time of the spread of agriculture and the rise of large social communities – big changes in diet and in exposure to communicable disease would be associated with those shifts.

In some respects the findings are cause for optimism. Global warming and rapid transformation of climate belts will expose billions of people to new experiences. Hundreds of millions, or more, may perish, yet our species’ evolution may speed up again. Let’s hope it leads to some improvement in avoiding self-induced misfortune.

See also: Holzman, D. 2007. How we adapted to a modern world. New Scientist, v. 196, 15 Dec 2007 issue, p. 8-9.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s