Speaker: Dr. Partha P. Majumder, National Science Chair, ANRF, Government of India

Date and Time: Wednesday, 16^th April 2025, 4.30 pm

Venue: CEP - 102/Mini-Auditorium

Title: Human History and Culture: Evolutionary Inferences from our Genomes

Abstract:

We have always been interested in questions about our past, such as, where do we come from? where did we move to and when? whom did we mix with? Traditionally, scientists of various disciplines – palaeontology, archaeology, prehistory, anthropology, linguistics – have used their own toolkits and have attempted to answer these questions. In this narrative, we shall focus on genomics as the toolkit. The genome provides continuity of biological information over generations. Thus, our genomes contain information about our history. This information can be exploited to reconstruct our evolutionary past.

I shall narrate the reconstruction of our evolution in two parts. The first part spans about five million years and the second one about two hundred thousand years. In the first part, the reconstruction of human evolution will be based primarily on fossil evidence. Genomic information will be used in the second part to reconstruct our evolutionary history after we evolved as modern humans, i.e., Homo sapiens sapiens. Modern methods of genomics have provided fantastic tools for the study of human history. Palaeontologists often have to base their inferences using fragmentary evidence – one broken bone, a skull or a jaw. Genome scientists, on the other hand, are able to gather vast amounts of heritable information by analysing DNA, in recent times by whole-genome or whole-exome DNA sequencing.

After modern humans evolved, we started to organize ourselves into groups. Resulting from this organization, our ‘mating structure’ also underwent reorganization. Instead of being one large inter-mating group, we started to choose mates from within “our own group.” This in turn resulted in genomic distinctions between groups. As a result of humans tending to mate within their own groups, genomic variations that arose in individuals within a group tended to remain within the group, since these variations had little chance to cross group-boundaries. This is because individuals carrying these variants did not generally mate with individuals of a different group. Genes, as we know, move with people. Therefore, if movement of individuals was restricted because they tended to remain within their own group, then genes also tended to have restricted movement. An individual usually avoids mating with another who does not share her or his own some physical, cultural and linguistic attributes. In other words, cultural and linguistic differences are barriers to admixture. In addition, geographical barriers also act as barriers to admixture. Since genomic changes appear in individuals within a group and these changes accumulate over time within a group, one expects that a contemporary group that has a lot of genomic diversity is an evolutionary “older” group, i.e., has evolved for a longer period of time. We shall use this paradigm and features to draw inferences on our evolutionary history and the spread of some cultural attributes of modern humans.