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However, there are millions of differences between humans and chimpanzees; our last common ancestor lived over six million years ago.
Recombination, also known as crossing-over, is the other main way DNA accumulates changes over time.
But in aggregate, over many generations, these changes lead to substantial evolutionary variation.
Scientists can use mutations to estimate the timing of branches in our evolutionary tree.
DNA holds the story of our ancestry – how we’re related to the familiar faces at family reunions as well as more ancient affairs: how we’re related to our closest nonhuman relatives, chimpanzees; how mated with Neanderthals; and how people migrated out of Africa, adapting to new environments and lifestyles along the way.
During recombination, the corresponding (homologous) chromosomes line up and exchange segments, so the genome you pass on to your children is a mosaic of your parents’ DNA.
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.
This tells them how long it’s been since the individuals shared ancestors.
Comparison of DNA between you and your sibling would show relatively few mutational differences because you share ancestors – mom and dad – just one generation ago.