Radiocarbon dating hominids
These “recent” events (in evolutionary time) include gene flow between distinct human populations, the rise of beneficial adaptations or the emergence of genetic diseases.
The case of Neanderthals illustrates how the mutation and recombination clocks can be used together to help us untangle complicated ancestral relationships.
Because mutations accumulate so slowly, this clock works better for very ancient events, like evolutionary splits between species.
The recombination clock, on the other hand, ticks at a rate appropriate for dates within the last 100,000 years.
It leads to shuffling of the two copies of the genome (one from each parent), which are bundled into chromosomes.
Applying the mutation clock to this count suggests the groups initially split between 750,000 and 550,000 years ago.
These changes accrue like the ticks on a stopwatch, providing a “molecular clock.” By comparing DNA sequences, geneticists can not only reconstruct relationships between different populations or species but also infer evolutionary history over deep timescales.
Molecular clocks are becoming more sophisticated, thanks to improved DNA sequencing, analytical tools and a better understanding of the biological processes behind genetic changes.
As recombination occurs in each generation, the bits of Neanderthal ancestry in modern human genomes becomes smaller and smaller over time.
Genetic changes from mutation and recombination provide two distinct clocks, each suited for dating different evolutionary events and timescales.At that time, a population – the common ancestors of both human groups – separated geographically and genetically.