A recent study published in Science is shedding light on a significant period in human evolution distinguished by a population bottleneck. The research provides valuable insights into the adversity our early ancestors faced and the genetic mutations that moulded modern humans. Scientists from China, Italy, and the U.S. have harnessed a new genomic analysis technique known as the Fast Infinitesimal Time Coalescent Process (FitCoal) to interrogate this bottleneck.
Understanding FitCoal and Its Implications
FitCoal is a scientific method for inferring ancient population sizes and demographic history by utilising modern-day human genomic sequences. It processes these sequences to calculate the composite likelihood for the site frequency spectrum (SFS), a distribution of allele frequencies within these sequences. FitCoal can identify severe bottlenecks and speciation events in human evolutionary history that are typically challenging to observe from the fossil record alone.
Cracking the Code with Genome Sequencing
Genome sequencing involves determining the order of DNA nucleotides or bases within a genome. This means figuring out the sequence of Adenine, Cytosine, Guanines, and Thymine that make up an organism’s DNA. A genome sequence provides a useful shortcut, facilitating scientists in finding genes more efficiently and swiftly. Although scientists are still learning to interpret these clues, a genome sequence does contain indications about the location of genes.
Main Findings of the Study: Population Bottleneck
The term “population bottleneck” refers to a drastic decline in a population’s size due to environmental incidents or human activities that kill off or inhibit a large segment of the population’s reproduction. This reduction hampers the genetic diversity and adaptability to changing conditions of the remaining populace. The study uncovers that a severe population bottleneck occurred between 800,000 to 900,000 years ago, pushing the human species close to extinction. During this bottleneck, only around 1,280 breeding individuals supported the whole human population, and this situation prevailed for about 117,000 years.
The Causes of the Population Bottleneck
Environmental Factors like glaciation events, changes in temperature and severe droughts were suggested as reasons for the decline in the size of the human ancestral population. The research proposes that humans endured in extreme conditions during the bottleneck period, approximately 930,000-813,000 years ago. The disappearance of other species, potentially food sources for early humans, also contributed to the bottleneck.
Genetic Diversity Loss and Its Impact
Early human ancestors suffered significant loss of life during the bottleneck period. This resulted in a substantial diminishment of genetic diversity, with an estimated 65.85% of humans’ current genetic diversity potentially lost during the early to middle Pleistocene era (from two million to 11,000 years ago).
Speciation Event: Formation of Chromosome 2
The bottleneck event in human evolution led to the fusion of two ancestral chromosomes, forming chromosome 2 in modern humans. This distinct trait is not found in other primates, making it a unique characteristic of human evolution.
Applying Genome Sequencing to Agricultural Practices
In connection to India’s agriculture, ‘genome sequencing’ can be implemented in the future by identifying disease resistance and drought tolerance genetic markers in various crop plants. Such use of genome sequencing can expedite the development of new crop varieties. It can also help decipher the host-pathogen relationships in crops, enhancing our understanding of crop diseases and their management.
