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The world's top biologists have met to discuss whether we should update evolution

Bringing Darwin's theory into the 21st century.

FIONA MACDONALD
28 NOV 2016
 

Evolutionary biology has helped scientists understand why the world looks the way it does for more than 150 years, since Charles Darwin released On the Origin of Species back in 1859. 

But a team of researchers has now proposed an update to our current understanding of evolution - one that could completely shift our understanding of how species evolve.

 

Some of the world's best known biologists just converged in London as part of a Royal Society meeting to discuss if it's time to upgrade one of the most fundamental theories in science.

To be clear, the researchers aren't saying there's anything wrong with our current theory of evolution. 

Instead, they want to update what we know so far with the latest discoveries in genetics and biology, because in recent years, we've realised that the human body is far more flexible, or 'plastic', than we ever realised - and it goes way beyond genes.

But before we go into the update, let's talk about the current accepted theory of evolution: modern evolutionary synthesis, or modern synthesis.

Modern synthesis merges Charles Darwin's famous ideas of natural selection with Mendelian genetics, which was developed by Gregor Mendel back in 1865 and laid out the subtle ways that we inherit traits through DNA.

This new modern synthesis was outlined in the 1930s and '40s, and quickly became the most widely accepted theory of evolution by the scientific community. It's the one we're all taught at high school today.

 

Basically, the modern synthesis states that evolution occurs via small genetic changes, that are regulated by natural selection.

This still holds true, even after decades of DNA research and human genome mapping. But new discoveries have also shown that changes can be passed down by more than just genes.

"The researchers don’t argue that the modern synthesis is wrong - just that it doesn’t capture the full richness of evolution," writes Carl Zimmer for Quanta magazine, who attended the Royal Society meeting from 7 to 9 November.

The researchers also argue that natural selection isn't necessarily the primary force in evolution - the limitations of development and the environments organisms live in can also play a role.

This new hypothesis of evolution is called the extended evolutionary synthesis, and it's been outlined in a paper in the Proceedings of the Royal Society B by researchers led by Kevin Laland, an evolutionary biologist from the University of St Andrews in Scotland. 

"It’s not simply bolting more mechanisms on what we already have," Laland explained to Zimmer. "It requires you to think of causation in a different way."

So what are these other ways that evolution can occur? In recent decades, scientists have shown that cells can use a range of molecules to control which of their genes are turned on or off, through a process known as epigenetics.

Basically, just having a gene isn't enough, you need it to be made into a protein to affect an organism. But epigenetic processes, such as methylation, can be used to stop that happening.

And researchers have shown that these epigenetic changes can actually be passed down, to allow offspring to better adjust to new challenges.

Epigenetic changes are more flexible than genetic changes, but they can have just as big an impact on the way an organism behaves or looks.

"The quality of food a woman gets while she’s pregnant can influence the size and health of her baby, and those influences can last until adulthood," writes Zimmer.

"What’s more, the size of a woman - influenced in part by her own mother’s diet - can influence her own children. Biologists have found that women with longer legs tend to have larger children, for example."

Modern synthesis doesn't account for those epigenetic changes, but extended evolutionary synthesis would.

And it could help explain some of the evolutionary mysteries in human history. For example, why so many fossils from the Homo genus that seemingly belong to the same species can look so similar in some ways, but so different in others - such as height and stature.

Extended evolutionary synthesis could also help to explain the birth of agriculture around 10,000 years ago.

We know that neolithic humans at the time started domesticating crops and animals, and transitioned from a hunter gatherer lifestyle to an agricultural one, laying the groundwork for modern civilisation.

But researchers have been puzzled as to how this happened, based on our understanding of modern evolutionary synthesis.

Modern synthesis would suggest that natural selection drove our ancestors to give up foraging and start growing crops instead, because it delivered the best payoff.

But growing crops would have taken a long time, and so scientists have struggled to explain how it would have initially benefitted our ancestors.

"You don’t get the immediate gratification of grabbing some food and putting it in your mouth," Melinda Zeder, an archaeologist at the Smithsonian Institute, told Quanta.

One hypothesis is that maybe the switch to agriculture occurred during a climate shift, when hunter gathering became harder than ever before. But there's been no evidence of that occurring.

Perhaps a better way of thinking about the transition is through the lens of extended evolutionary synthesis - maybe humans, not natural selection, steered their own evolution, and simply decided to start farming, whether or not there was initial payoff.

This is a process known as niche construction, where an organism adapts to their environment in new ways that don't necessarily have anything to do with genetics. Those changes can be passed down, and can shift the rest of the environment as a result.

Of course, extended evolutionary synthesis still has its critics - there were several talks at the latest meeting arguing against the need to update modern synthesis just yet.

So for now, extended evolutionary synthesis is just a hypothesis, and while there have been a lot of great minds thinking about how it could work, we need more evidence to figure out if it actually works.

"This is likely the first of many, many meetings," Laland told Zimmer. "It’s doing the research, which is what our critics are telling us to do. Go find the evidence."

You can see a full write-up of extended evolutionary synthesis in Proceedings of the Royal Society B.

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