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

Subject :Science and technology

Section: Msc

Introduction

In November 2022, the global human population surpassed eight billion, highlighting our dominant presence on Earth.
Our dominance is attributed to cognitive abilities, technology, and environmental reshaping, but it has led to habitat destruction, pollution, and climate change, endangering species.

Human Evolution and Genomic Insights

Genomic data and fossils provide profound insights into human evolution.
Ancient DNA has preservation limitations, offering recent insights.
Computational tools analyze genome sequences, mitochondrial DNA, and the Y chromosome, extending understanding across time scales.
These tools identify population bottlenecks, founder events, and genetic disease origins.

Population Bottlenecks, Founder Effects, and Genetic Diversity

Population Bottlenecks:
- Occur when a population is sharply reduced in size, often due to catastrophic events or environmental changes.
- The genetic diversity of the population significantly decreases, as only a small number of individuals survive and reproduce.
- Bottlenecks reduce numbers, leading to founder effects.
Founder Effects:
- Genetic phenomena occur when a small group of individuals, or founders, establishes a new population in a different geographical area or under isolated conditions.
- These founders carry only a subset of the genetic diversity present in the larger source population.
- The new population inherits a limited range of genetic traits, often resulting in increased frequencies of specific traits or genetic diseases among their descendants.
Examples of Founder Populations:
- A small group of individuals gave rise to the modern Ashkenazi Jewish population, leading to a higher prevalence of certain genetic diseases in this group.
- Similarly, Indian endogamous groups, formed through strict marriage practices, have shared genomic stretches due to inbreeding, resulting in specific genetic traits being more common within these populations.

Near-Extinction Event in Human History

Recent computational research challenges prior human origin estimates.
Around 1,200 founding ancestors are proposed, contrasting earlier estimates of 100,000.
The bottleneck occurred about 900,000 years ago, lasting over 100,000 years.
This bottleneck coincided with significant climate changes, potentially affecting species survival.
Recovery may be linked to improved conditions, fire use, and agriculture.
The prolonged small breeding population likely influenced human genetic diversity and evolutionary outcomes.