Speciations or a Sudden Origin?

Genomic analysis is yielding immense amounts of data about the evolution of all the species we’ve sampled. Some of the chronological results require some care when sharing with the general public, else they can be paraded as ‘proof’ of more mythological origin tales. A recent example comes from the work of David Thaler. Here’s a paper from 2014:

DNA Barcoding Works in Practice but Not in (Neutral) Theory

More recently there’s this particular 2018 paper:

Why should mitochondria define species?

Which gets this write up on the Intelligent Design web-site “Evolution News” of:


New Paper in Evolution Journal: Humans and Animals Are (Mostly) the Same Age?

And a somewhat less restrained write-up in the Murdoch Press:

Why did the overwhelming majority of species in existence today emerge at about the same time?

It seems both write-ups didn’t read much past the abstract. Of course, the pro-Science web-sites had to respond with more explanatory explanations of what the findings really meant…

No, Humans Are Probably Not All Descended From A Single Couple Who Lived 200,000 Years Ago
Did 90% of Animal Species Appear about the Same Time as Human Beings?

My initial reaction was to ignore the breathless reportage and contact David Thaler himself. He emphasised that the chief thesis of the paper – and the 2014 paper before it – was to argue that species are biologically real entities, defined well by their mitochondrial genomes. The suggestion is that humans – and other species – derive from small founder populations and, thus, singular mitochondrial lineages. But does that argue for Noah’s Floor or Adam & Eve in a Garden of Eden?
Here’s Thaler’s eloquent response to deriving that conclusion from his work on DNA barcodes…

To say that our paper is evidence for Noah’s ark is like saying that it is evidence for the moon being made of cheese or the earth being flat since we do not provide evidence against these ideas. Scientific discourse is not free of rhetoric but we hold out the hope that it can be at a higher level.

He goes on to explain that the variance within species is quite ‘variable’ and the molecular clocks that give estimates for origin times for the individual mitochondrial species barcodes are hard to calibrate. Thus while species largely show the same pattern of ‘singular’ origin, their origin times vary across the past few hundred thousand years. What the genetic barcodes imply is that species remain intact at a genomic level, with some form of selection suppressing variation. Not so strange in the context of “Punctuated Equilibrium” – a once controversial viewpoint of the 1970s-80s, but largely absorbed into the mainstream by the 1990s.

Even in the human fossil/DNA record there’s ample signs of this – just 300,000 years ago at least five ‘species’ of ‘Homo’ (our biological genus) are known: Homo sapiens (appeared c. 300,000 years ago), Homo neanderthalis, Homo naledi, Homo floresiensis and the enigmatic ‘Denisovans’ who are only known from genomic fragments in ancient remains and modern humans. We know that Sapiens, Neanderthals and the Denisovans interbred, but what was our relationship with the smaller brained Naledi and Floresiensis? And, even after that mixing, one lineage came to dominate. Only further molecular studies of just how mitochondrial mutation affects selective advantage will clarify the mechanism of how species appear and then remain distinct from their close kin.