Wednesday, 13 October 2021

Evolution News - What makes us Different to the Chimpanzees and Why it Should Bother Creationists

What makes us human? The answer may be found in overlooked DNA | Lund University.

Sometimes you just have to laugh at Creationists, the knots they have to tie themselves into to try to make their childish superstition match what real-world evidence shows.

This paper, for example, which argues that the functional genetic difference between humans and the chimpanzees is to be found, not so much in the 2% of the genes by which we differ from them, but in how the 'junk' DNA is used by the them and us.

Creationists, of course, hate the statistic about us sharing 98% of our DNA with chimpanzees, and the intelligent [sic] design cult hates the fact that so much of our DNA is junk and so evidence against design, intelligent or otherwise. They would normally be jubilant over a finding like this that shows at least some of it might make a functional difference, so is not strictly junk after all - until they realise that that function is all that separates us from the chimpanzees.

The open access paper in the on-line journal, Cell Stem Cell is by a team of scientists led by Johan Jakobsson, professor of neuroscience at the Wallenberg Neuroscience Center and Lund Stem Cell Center, Lund University, Sweden, together with colleagues from Washington University, USA and Ecole Polytechnique Fédérale de Lausanne, Switzerland. Lund University's news item explains:
Instead of studying living humans and chimpanzees, we used stem cells grown in a lab. The stem cells were reprogrammed from skin cells by our partners in Germany, the USA and Japan. Then we examined the stem cells that we had developed into brain cells

The part of our DNA identified as different was unexpected. It was a so-called structural variant of DNA that were previously called "junk DNA", a long repetitive DNA string which has long been deemed to have no function. Previously, researchers have looked for answers in the part of the DNA where the protein-producing genes are – which only makes up about two per cent of our entire DNA – and examined the proteins themselves to find examples of differences.

This suggests that the basis for the human brain’s evolution are genetic mechanisms that are probably a lot more complex than previously thought, as it was supposed that the answer was in those two per cent of the genetic DNA. Our results indicate that what has been significant for the brain’s development is instead perhaps hidden in the overlooked 98 per cent, which appears to be important. This is a surprising finding.

I believe that the brain is the key to understanding what it is that makes humans human. How did it come about that humans can use their brain in such a way that they can build societies, educate their children and develop advanced technology? It is fascinating!

Professor Johan Jakobsson
Professor of neuroscience
Lund University
Our DNA is very similar to that of the chimpanzee, which in evolutionary terms is our closest living relative. Stem cell researchers at Lund University in Sweden have now found a previously overlooked part of our DNA, so-called non-coded DNA, that appears to contribute to a difference which, despite all our similarities, may explain why our brains work differently. The study is published in the journal Cell Stem Cell. The chimpanzee is our closest living relative in evolutionary terms and research suggests our kinship derives from a common ancestor. About five to six million years ago, our evolutionary paths separated, leading to the chimpanzee of today, and Homo Sapiens, humankind in the 21st century. In a new study, stem cell researchers at Lund examined what it is in our DNA that makes human and chimpanzee brains different – and they have found answers.

[…]

Using the stem cells, the researchers specifically grew brain cells from humans and chimpanzees and compared the two cell types. The researchers then found that humans and chimpanzees use a part of their DNA in different ways, which appears to play a considerable role in the development of our brains.

[…]

The new findings thus indicate that the differences appear to lie outside the protein-coding genes in what has been labelled as "junk DNA", which was thought to have no function and which constitutes the majority of our DNA.
Professor Jakobsson is clearly of the opinion that what materially separates us from the chimpanzees, is not the superficially obvious but relatively minor anatomical differences, but in the way our brain develops and functions, giving us far greater information processing power, and that, surprisingly, this difference may be due to the role played by 'junk' DNA in brain cell growth and organization.

In their open access paper, the team say:
Graphical abstract
Highlights
  • ZNF558 is uniquely expressed in human but not chimpanzee forebrain progenitors
  • ZNF558 has been co-opted to control the expression of a single gene, SPATA18
  • ZNF558 plays a role in mitochondrial homeostasis and brain development
  • ZNF558 expression is controlled by the size of a downstream VNTR


Summary

The human forebrain has expanded in size and complexity compared to chimpanzees despite limited changes in protein-coding genes, suggesting that gene expression regulation is an important driver of brain evolution. Here, we identify a KRAB-ZFP transcription factor, ZNF558, that is expressed in human but not chimpanzee forebrain neural progenitor cells. ZNF558 evolved as a suppressor of LINE-1 transposons but has been co-opted to regulate a single target, the mitophagy gene SPATA18. ZNF558 plays a role in mitochondrial homeostasis, and loss-of-function experiments in cerebral organoids suggests that ZNF558 influences developmental timing during early human brain development. Expression of ZNF558 is controlled by the size of a variable number tandem repeat that is longer in chimpanzees compared to humans, and variable in the human population. Thus, this work provides mechanistic insight into how a cis-acting structural variation establishes a regulatory network that affects human brain evolution.

What a dillema for Creationists! Do they dismiss the entire thing because it talks about how we differ from our closest evolutionary relatives, or do they wave it jubilantly as evidence that not all junk DNA is without function?

Thank you for sharing!









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