Genomic clues suggest humans’ ancestors nearly went extinct 9L years ago Premium

Genome sequencing has enabled researchers to uncover population bottlenecks, founder events, and the age of genetic diseases in the history of human evolution and migration. Ancient DNA recently revealed a super-bottleneck in human evolution 900,000 years ago, which could have shaped humanity in ways we don't yet know. Genomic analysis is like a time-travelling telescope, providing insights into our species' future.

The human population on the earth exceeded eight billion people in November 2022, underscoring our species’ status as the dominant force on our planet, with our unparalleled cognitive abilities and technological prowess, and ability to harness, engineer, and reshape the environment around us.

This dominance has also resulted in some catastrophic outcomes as we have expanded our footprint, resulting in habitat destruction, pollution, and climate change, pushing a number of species to the brink of extinction. It is hard to imagine that we as a species, just like other animals and plants, could have also been pushed to the brink of extinction at multiple points in the entire history of evolution.

Think about a scenario where the whole human species is represented by a few members only, living in a very hostile natural environment where everyday existence is at the mercy of natural forces. This small group, in addition to its extraordinary resilience and creative survival tactics, would have had the enormous responsibility of keeping the entire human species alive. It’s quite possible that our ancestors could have experienced many such species-defining moments on their path to dominating the world as we know it today.

Researchers have been interested in understanding the evolution and history of the human species, and genome sequences have proved to be of tremendous help. Together with evidence like fossils, researchers have been able to piece together parts of human evolution and history in astonishing detail. However, ancient DNA is limited by the timeline: it can offer only recent insights into human evolution; DNA older than that is seldom preserved intact.

Our ability to sequence human genomes so quickly and computational tools to analyse the data has allowed us a near-pristine view of the past. This is because genome sequences offer a sort of a snapshot of the molecular clock of human evolution. The genome accumulates genetic variations at a constant rate; the recombination and exchange of genetic material also occur at the time of generation of gametes (sperm and ovum).

There have also been insights from the sequences of the mitochondria and the Y chromosome, which are passed on matrilineally and patrilineally, respectively.

Taken together, scientists have developed several computational approaches to piece together how humans evolved, and have been able to extend them to timescales far beyond those afforded by ancient DNA. They have thus been able to identify population bottlenecks and founder events as well as determine the age of many genetic diseases.