Home Awesome & Weird Modern Humans Have Less DNA than Ancestors – ‘May Be We Devolved,’ Scientists Say!

Modern Humans Have Less DNA than Ancestors – ‘May Be We Devolved,’ Scientists Say!

by Sankalan Baidya
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An interesting turn of events has left modern scientists puzzled and they have started pushing forward the question – “Are We Devolving?”

In a study, scientists found that modern humans have less DNA compared to ancient ancestors. Science – a popular journal, published the study where it was revealed that long back when we, the modern humans, headed for the different direction from our ape ancestors, we lost a substantial amount of DNA. According to the study, our ancient ancestors had more genetic information and surprisingly, we don’t have that information anymore! This is where the scientists asked, “Are we devolving?”

An international team of geneticists from 39 institutes from around the world embarked on the incredible mission of genome sequencing. Professor Evan Eichler from University of Washington’s Department of Genome Sciences led the team of geneticists who sampled 236 people covering 125 different populations. The result? The most diverse genetic map ever produced till date!

map of human populations sampled for genome sequencing

Map of 125 different populations sampled and the relationship between each other.

Once the whole sequencing was completed, the team was surprised to find that 40.7 million DNA base-pairs were missing in Homo sapiens since they separated out from the common ancestor from which the chimpanzees (our closest living ancient ancestor today) evolved too!

Though 40.7 million DNA base pairs were lost, scientists say that only 27.96 million out of the 40.7 million were actually unique and the others were just repeated sections. Nonetheless, scientists say that eventually we lost several thousands of genes. However, scientists do say that most of the lost DNA possibly did not have any real function.

It all started in Africa, some 13 million years ago when we separated out early apes during our early stages of evolutionary history. That is when we lost the first set of 15.8 million unique base pairs. After the initial separation, humans started spreading out in different areas on a global scale. This is when the second round of loss kicked in and we ended up losing another set of unique DNA base pairs. This time, the loss was slightly less at 12.16 million base pairs.

According to Professor Evan Eichler, once separate from apes and moving out of Africa, humans experienced a massive population loss. This, according to Eichler, played an instrumental role in a significant amount of DNA loss.

Eichler mentioned in the report that the sheer magnitude of the data set achieved from genome sequencing allowed the whole team to chart the genome sequence of the ancestral humans and identify the DNA pairs lost when human migration started. He said that the team anticipated that Africans will possess more of ancestral genomes compared to non-Africans and they were right.

He went on explain the whole DNA makeup, the gist of which is listed below:

  • There are 3 billion DNA base pairs in human genome.
  • All these pairs live in just 23 chromosomes.
  • All these 23 chromosomes can be found at the very center of every single cell that can be found in human body.
  • An average gene that is found in human genome consists of nearly 765 DNA base pairs.
  • So, if 27.96 unique DNA base pairs were lost, then at least 37,000 genes were lost during the evolutionary phase over the last 13 million years.

The scientists first sequenced the genome of the 236 test subjects (belonging to different populations) randomly selected from the world. The genome sequences were then compared against the genome sequences from orangutans, chimpanzees and genome sequences derived from human species like Denisovans and Neanderthals.

The derived results helped to bring the round-the-globe human migration complexity into focus. This were complex simply because our ancient ancestors were involved in inter-species breeding for some reason or the other.

During the research, the scientists also found DNA segments which were duplicated in now extinct Denisovans and those duplicated segments can now be found in modern humans mostly in oceanic populations, for example, islanders of South Pacific. This is what led the scientists to believe that Denisovans interbred extensively with modern humans some 40,000 years ago. The researchers estimate that duplication of sections of chromosome in Denisovans occurred some 440,000 years ago.

chromosome duplication in ancient denisovans

A DNA segment (chromosome 16) in Denisovans’ genome that was duplicated some 440,000 years ago and then spread because of interbreeding with modern humans some 40,000 years ago.

Neanderthals had at least 104,000 DNA base pairs that are currently not found in modern humans. Alternately, modern humans have 33,000 DNA base pairs that were not present in Denisovans and Neanderthals. This led the scientists to conclude that even our ancient ancestors who are now extinct also experienced DNA loss!

genetic tree showing relation between human populations based on deletion

Genetic tree showing how human populations are related based on genome deletion. Everything started from Denisovans and Neanderthals shown far out on left.

So, now that scientists have shown that modern humans have lost significant amount of DNA, the question they ask is, “are we evolving or devolving?”

They haven’t answered this question yet because they don’t know.

We, the idiot commoners on other hand have long believed that evolution has put us on top of the animal kingdom and we actually give all the credit to our hands, which are unique and allow us to use tools in ways that no other animals are capable of.

Unfortunately, recent scientific studies reveal that hands we possess are actually far more primitive than we think. In fact, our closest living ancient ancestors – the chimpanzees have far more evolved hands. Chimps, over time, evolved to have longer fingers but we continue to share the almost same hand structure and shape to that of the common ancestors that both chimps and we shared.

There are many questions that still require answer. For instance, why did modern humans survive and other human species died out? We lost DNA. What happens next? We lose more? Then what? Possibly… more loss followed by more… actually, all we can do is speculate and hope that more research in this area will help us find answers about our evolutionary history and our evolutionary future.

Sources: mailonline, ancient-origins, gizmodo

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