New research into genetics has uncovered a startling fact; ancient humans were very close to extinction a million years ago.
According to Lynn Jorde, a geneticist studying human development at the University of Utah in Salt Lake City, the genetic evidence suggests that early human species, which include Homo erectus, Homo sapiens and Homo ergaster and a total population of perhaps 55,500 individuals, faced a major setback concerning diminished genetic diversity about one million years ago.
In the words of Jorde:
“We’ve gone through these cycles where we’ve had large population size but also where our population has been very, very small.”
Even though the fossil evidence seems to indicate the expansion of the Homo genus species into Africa, Asia and Europe, Jorde’s current study, the findings of which are detailed in the January 18 issue of the Proceedings of the National Academy of Sciences, suggest that the genetic diversity of the population was seriously challenged.
Jorde made his estimates by scanning two modern human genomes (the entirety of an organism’s hereditary information) for a type of mobile element called Alu sequences. These short snippets of DNA appear with low frequency between the diverse regions of the genome and suggest an ancient, prehistoric presence. The team was able to use a concept known as nucleotide diversity, which is used to measure the degree of polymorphism within a population, to estimate the age of a particular region. The process involves studying the older Alu-containing regions, which have accumulated more mutations over the course of centuries. The estimated difference in population size and genetic diversity between modern and early humans was deduced by comparing the nucleotides in these old regions with the diversity in the two genomes.
The human genome is the genome of Homo sapiens, which is stored on 23 chromosome pairs.
According to Cédric Feschotte, an evolutionary geneticist at the University of Texas:
“This is an original approach because they show that you can use mobile elements…to flag a region of the genome.”
Scientific windows into our ancient past shed much light on unexpected things that modern civilization sometimes forgets; namely, how small we all look standing against the ocean and the stark vulnerability of our ancestors.
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