A Strange New Paternal Lineage

[Update: Waking up this morning I find that the ICR article this was based on has vanished (it may still return at a later date). I have a zotero capture if anyone wants a full copy of it.] [Update #2: It is indeed back now, and I’ve added a TL;DR summary at the bottom.]

In mammals (including humans) most DNA gets mixed together as it gets passed on from generation to generation: chromosomes come in pairs, one from the mother and the other from the father; but when sperm and eggs are produced these chromosomes swap segments, and the chromosome that ends up in a given sperm or egg is entirely random. There are two exceptions to this rule. Mitochondrial DNA (mtDNA) can only be inherited from the mother – though both sexes have it – while the “Y chromosome” is only passed down from father to son.

This property makes these two varieties of DNA extremely useful in tracing ancestry, as distinct lineages can be found and compared. When these lineages are traced backwards they can only merge, never split, and thus will eventually converge to a point. The human mitochondrial genome has famously been traced back to “Mitochondrial Eve,” who lived between somewhere 140 and 240 thousand years ago, probably in Africa. “Y-chromosomal Adam” (which doesn’t roll off the tongue quite as well) meanwhile is only dated to around 60 to 140 thousand years before the present, but lived on the same continent.

The Denisova …Human?

The Denisova hominins were a group of humans that, similar to the more famous Neanderthals, survived until just a few tens of thousands of years ago. Their discovery was announced only in 2010, in the form of a portion of a child’s little finger extracted from the Denisova cave in Siberia. Since then it has been determined that a tooth found in 2000 was from the same group. Curiously, given the finds location in Russia, the Denisovans are believed to have interbred with the ancestors of people that now live in the vicinity of Melanesia.

We can tell all this from such scant evidence because conditions in the cave allowed the aforementioned finger bone to preserve the complete genome of its owner. Most recently this has been sequenced with as much fidelity as you would get from an analysis of a living person. Brian Thomas writes: Is Fossil Finger Genome Human?

The Denisovans are similar enough to modern humans that creationists must include them on our side of their rather arbitrary human-ape division. They have inherited the “fully human” epithet of the Neanderthals. For example: