This skull belonged to a man living around the year 7500 BC in southern France, and probably resembles the skull of the ancient man whose skeletal DNA was sequenced. Source: Wikimedia Commons (photographed by Günter Bechly)

This skull belonged to a man living around the year 7500 BC in southern France, and probably resembles the skull of the ancient man whose skeletal DNA was sequenced. Source: Wikimedia Commons (photographed by Günter Bechly)

For much of its history, biological anthropology was largely been based on guesswork, drawing conclusions about ancient humans’ physiology from skeletal details alone. These skeletons tended to be incomplete, missing anywhere from a few long bones to everything but a few pieces of a skull. These incomplete findings caused debates in the field, with almost no hope of resolution.

The advent of whole-genome sequencing, along with gains in sequencing efficiency allowing researchers to read the entirety of an organism’s genome from a single cell, have drastically changed the field of biological anthropology (1). The promise of genomic sequencing was finally realized this year, when a team published a full Neanderthal genome based on samples from a 50,000-year-old toe bone (2).

These advanced identification and analysis methods have allowed researchers to make more evidence-based inferences about our long-dead ancestors. Last week, an international team published results in Nature detailing inferences made from the sequencing of a complete genome of a 7000-year-old pre-agricultural anatomically modern human in northwestern Spain (3).

The group isolated DNA from the remarkably well-preserved tooth of a skeleton found in a cave located high in the Cantabrian Mountains of northwestern Spain. The tooth had almost half of its original DNA intact, enough to allow for the sequencing of over 85 percent of the original genome (3).

The final sequence was then cross-referenced to the 1000 Genomes Project, a database of 1092 full modern genomes, to identify differences between ancient and modern genes. This data can provide information regarding the phenotypes of ancient humans by finding similar genetic variants in the same genes (3).

Upon further analysis, the team discovered that the ancient human had intriguing variants of the genes SLC45A2 and SL24A5, which affect skin pigmentation. These specific variants can be found in populations around the world, all with relatively dark skin, indicating that this ancient European may have had a similar skin tone. The gene HERC2, which codes for eye color,was also analyzed, and the team found that this specimen would also have likely had blue eyes. The skeleton’s DNA also had genes that code for immune proteins similar to our own (3).

These findings have two important implications. The first is that the traditional ‘European’ phenotype of fair skin and blue or green eyes did not come into being all at once. Instead, eye color was the first trait to change in European populations (3). The second implication challenges the view that increased exposure to animals strengthened human immune systems in an adaptive manner (4). This genome shows that many immune proteins from pre-agricultural humans remain unchanged today (3).

While these findings reveal important details about early humanity, care must be taken to remember that this is but one skeleton. To confirm these findings, similarly ancient genomes from elsewhere in Europe must also be examined.

References

1. Tawy, N. Nature Methods. 11, 18 (2014).

2. Prüfer, K. et al. Nature.505,43-49 (2014).

3. Olalde I. et al. Nature. (in press) (2014).

4. O. Galor, O. Moav, The Neolithic Revolution and Contemporary Variations in Life Expectancy (2007). Available at http://www.brown.edu/Departments/Economics/Papers/2007/2007-14_paper.pdf (30 January 2014).