Category Archives: Human evolution

South Americans – only one wave of settlers?

Nature reports: The meeting of the Society of American Archeology listened to Dr. Fehren-Schmitz, who presented the sequencing of human bone found in Peru at a site called Lauricocha. The remnants are from five individuals, two of them died around 9000 years ago, a third 2.500 years later and another a further 2300 years later, the fifth was dated. The sequences were derived from mitochondria and from the Y chromosome.

The results are in agreement with a single wave of migration. There might be earler migration but not necessarily. It is now up to investigator to sequence the actual indigenous population to see whether there are dicrepancies to this determination

Studies on the Epigenom in Human Early Embryos

Epigenetic modification of DNA, mostly methylation, is the way which ensures lineage specity in mammalian organization and propagation of cell types. It is inherited while cells multiply.

In Nature this week (doi:10.1038/nature13648) Reik and Kelsey describe two article (Guo, H. et al. Nature 511, 606610 (2014) and Smith, Z. D. et al. Nature 511, 611615 (2014)) where the methylation patterns in egg, sperm, fertilized eggs and blastocysts are analyzed. As has been found in mice before, blastocysts lose most of their methylation. Later in development the DNA gets remethylated again. This has been suggested but formal proof was lacking. The imprinting – methylated gene regions due to maternal or paternal origin – is not as much removed for maternal genes, but for paternal ones.

Whether these papers will improve human stem cell research is to be seen.

When Africans met Neanderthals some 50000 years ago: war and rape

There is an very interesting paper in Nature (doi:10.1038/nature12961) about the Neanderthal genom part in modern men. It shows an a chromosome by chromosome demonstration how much of the Neanderthal ancestry is found in the autosomes and in the sex chromosome: about 1 % in autosome and considerable less in sex chromomes. In the Y-chromosome it is barely found.

When the two populations first encounterd some 50000 years ago (as a paper form PLOS suggested: DOI: 10.1371/journal.pgen.1002947) we can envisage how this was done:  there was war and the Neanderthal female were raped after the man were killed. Whether this was a singular event or repeatingly done in the clash of general war betweem the two species is not documented, but when the progeny e.g. was selected for the “African” phenotyp then the Neatherthal would be not maintained in the Y chromosome.

Very suggestive! And much has not changed till modern times

The early history of man

A review in Science (DOI: 10.1126/science.1236828) deals with the human evolution 3 to 1.5 x 106 years ago. The aridity in Africa is supposed to drive expansion to other continents. Several parallel  lineages were present. You may find this review  at the local university or in an (English) bookshop.

Tibetans are different!

A paper in Nature (Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA Emilia Huerta-Sánchez, Xin Jin, Asan et al.) says that DNA in Tibetans to adapt to the altitude can be attributed to an extinguished hominid precursor, the Denisovan: (cited from Nature)

Admixture with other hominin species helped humans to adapt to high-altitude environments; the EPAS1 gene in Tibetan individuals has an unusual haplotype structure that probably resulted from introgression of DNA from Denisovan or Denisovan-related individuals into humans, and this haplotype is only found in Denisovans and Tibetans, and at low frequency among Han Chinese.