Map showing the locations and sample sizes of sites from which yak X genomes were generated. Extant wild yak distribution is in light orange.16 Elevation is shown. Map not to scale.
For young-Earth creationists, the problem with ancient DNA is that it keeps revealing histories which their preferred chronology cannot accommodate. The latest example is an extinct relative of the yak whose evolutionary separation from living yaks began at least 400,000 years ago — long before the supposed “Creation Week” of a literal reading of Genesis. Its existence has emerged from fragments of Siberian bone too incomplete to identify by their shape, but which retained something much more informative: genetic evidence of a lost branch of the bovine family tree.
In a study published in Current Biology, Jonas Oppenheimer, Alexandre Gilardet and colleagues report 20 ancient nuclear genomes from Denisova Cave and other sites in southern Siberia, spanning more than 200,000 years. The lineage, provisionally known as “yak X”, had previously been recognised from mitochondrial DNA. The new analysis provides much broader genetic evidence that it represented a distinct species that effectively separated from the lineage leading to living yaks by about 250,000 years ago.
This was no static population inhabiting an unchanging world. The genomes reveal a demographic decline and suggest population turnover, accompanied by reduced genetic diversity, around the last interglacial, approximately 130,000–115,000 years ago. Warming may have disrupted the distribution of these cold-adapted animals; an earlier warm interval may also have helped isolate populations during their initial divergence. Those climatic explanations remain hypotheses, but the genetic evidence provides a record against which they can be tested. The youngest specimen analysed is about 27,000 years old; precisely when, and why, the lineage subsequently disappeared remains unknown.
There is an equally instructive lesson in the researchers’ caution. Although they interpret the genomic evidence as identifying a separate species, they have not simply attached a new formal species name to these fragmentary remains. Comparisons with previously described yak-like fossils are needed to establish whether the genetic lineage corresponds to an animal already recognised from its anatomy. Discovering a previously unrecognised genetic history and resolving its taxonomic identity are related but distinct tasks. Scientific confidence in one does not require pretending that the other has already been settled.
For creationism, meanwhile, calling the animal “just another member of the cattle kind” does nothing to resolve the chronological problem. The evidence concerns a branching history of populations, divergence and eventual extinction extending across hundreds of thousands of years. Evolutionary biology supplies the framework for reconstructing that history and asking further questions about it. Compressing everything into a few thousand years would require an alternative explanation for the genetic relationships, the ages of the remains and the succession of populations — not merely a biblical label applied after the evidence has been collected.





































