Model offers insight into how life continues to evolve

modeling evolution
In the new model of evolution, polymers can form new polymers of different lengths via an enzymatic ligation process, as shown here. Credit: Worst et al. ©2016 IOP Publishing
(Phys.org)—One of the most puzzling things about evolution is that, even after 4 billion years, it hasn't stopped. Instead of culminating in a single best adapted species, today the Earth contains an estimated 8.7 million different species, all of which will one day die out as a variety of new species takes their places.

Although scientists have tried to model these evolutionary dynamics in the lab, such as by using systems of molecules that change over time in some way, most of these models eventually generate a single dominant species and then come to a standstill. Scientists still don't completely understand how evolution continues to generate new species, which is known to occur even in the absence of changing external pressures.

Now in a new study, a team of physicists has developed a theoretical and experimental model of evolution that continues without end, even under constant external conditions. The model may help scientists better understand how the biosphere continues to evolve over billions of years.

"We hope to understand the necessary conditions of Darwinian statistics—notably, the coexistence of species that each have a finite lifetime—that emerge with Darwinian evolution," coauthor Albrecht Ott at Saarland University in Saarbruecken, Germany, told Phys.org. "This seems a major problem that research on the origin of life needs to deal with. Furthermore, molecular systems can help to elucidate mechanisms of speciation, notably the emergence and disappearance of niches."

The new model system consists of linear DNA polymers of different lengths, where the length of a polymer determines its "species." The polymers can reproduce (creating polymers of the same length) or join together via the polymer-binding enzyme DNA ligase (creating longer polymers, which are new species).

In their experiments, the researchers started with polymers that were 10 or 20 base pairs long. After exposing them to temperature variations that promoted reproduction and binding to various degrees, the researchers found that polymers of different lengths began to emerge.

modeling evolution
In the new model, different species (lengths of polymer) emerge for a time, and then “die out” as new species take their place; there is no permanent dominant species. Credit: Worst et al. ©2016 IOP Publishing

The results revealed that species evolution depends on which growth mechanism dominates. In situations in which the ligation mechanism dominates, all possible polymer lengths are generated (all multiples of 20 starting with a length of 20, such as 40, 60, 80, and 100 base pairs and above).

But when reproduction dominates, only certain lengths appear (specifically, lengths of 10, 20, 40, 80, or 160 ), and only for limited periods of time. Each polymer length follows a pattern in which its numbers exponentially increase, then plateau, and finally decrease, allowing new lengths of polymers to emerge.

In these reproduction-dominant situations, the evolution of polymers of different lengths bears similarities to Darwinian evolution. As the researchers explain, it is the dynamics of the entire system that selects a particular, new species (length of polymer) in such a way that it can use the existing situation most efficiently to multiply. Each time, the system escapes from this dominance by creating a that uses the new situation to its benefit.

"We believe that we have created a model system that exposes a dynamic mechanism reflecting essential traits of Darwinian evolution," said coauthor Karsten Kruse at Saarland University. "In a reproduction-dominated situation, in our system, only certain types of molecular reproducers occur: those that benefit most from a given situation. However, these 'species' fail to dominate the situation because of the emergence of ever new other species."

In the future, the researchers plan to modify the model so that the molecules acquire functionality, making them more similar to biological species.

"Although the simplicity of our system is what constitutes its quality and makes the message so clear, it is unclear how to devise a more complex system that enables new functionalities in a Darwinian setting," Ott said. "This is something we plan to address in the future."


Explore further

When it comes to polymer fragility, size does matter

More information: Emanuel Gregor Worst et al. "Unbounded growth patterns of reproducing, competing polymers—similarities to biological evolution." New Journal of Physics. DOI: 10.1088/1367-2630/18/10/103003
Journal information: New Journal of Physics

© 2016 Phys.org

Citation: Model offers insight into how life continues to evolve (2016, November 8) retrieved 19 June 2019 from https://phys.org/news/2016-11-insight-life-evolve.html
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Nov 08, 2016
If you do not know how life arose on earth in the first place, no amount of Darwinian evolutionary research is going to help.

Life did not "evolve" from a single ancestor - that is simply impossible - giving rise to a "tree" of evolution, but was created in a vast flat "bush" of separate lifeforms each within its own unique kind.

As we can see today, there is no Darwinian evolution happening, rapid speciation and variation within a kind, yes, Darwinian evolution, NO. It has always been like this since the beginning of creation.
One has only to look at the impossibility of separate sexual organs and systems developing in a single species and then splitting up into the different genders within that kind to see that that represents just one item that makes Darwinian evolution a complete wash.

These researchers are simply chasing their own tails.

Nov 08, 2016
So, It is highly imperative that Humans to Intrude & Solve it.
Photosynthesis + No Violence Tools + Removal of ALL Carnivores + etc., etc., etc., FEATURES into What else? Into ALL Surviving Species of the Future!
If you Can't eat Plants alone, you go Amoeba, Fish, Fox!
Of course, Don't Start to Meddle Right Away;
Just Wait until Acquiring of ALL knowledge of Metabolic Pathways Task is Accomplished TOTALLY!

Nov 08, 2016
One of the most puzzling things about evolution is that, even after 4 billion years, it hasn't stopped. Instead of culminating in a single best adapted species

It might have stopped if the environment were static. But species take resources out of the environment which they use for food/shelter/etc.
Add to that the fact that the most extreme competition comes from individuals of the same species - so even a species that doesn't alter it's environment much will start to alter it in an increasing manner with an increase in number of individuals.
I.e. the mere presence of an (even optimally adapted) species alters the environment to a point where further adaptation provides a better fit.

In summary: why should we expect evolution to stop? (Natural) evolution will only stop once individuals have become immortal. Artificial evolution need not stop even then.

Nov 08, 2016
As we can see today, there is no Darwinian evolution happening, rapid speciation and variation within a kind, yes, Darwinian evolution, NO. It has always been like this since the beginning of creation.
One has only to look at the impossibility of separate sexual organs and systems developing in a single species and then splitting up into the different genders within that kind to see that that represents just one item that makes Darwinian evolution a complete wash.

Your examples would simply be a strong argument that sexual repro developed BEFORE any other major speciations...

Nov 09, 2016
Your examples would simply be a strong argument that sexual repro developed BEFORE any other major speciations...

Please, man, sexual differentiation was there right from the start. Male and Female. There wasn't any single ancestor from which to "evolve" in the first place. Everything was created with the right gender or non-gender in place right at the start.
The Darwinian paradigm is based on a religion of myths in pre-historic times, i.e. there is no eye-witness account and hence no historic record as to what supposedly happened - it's pure myth.

Nov 10, 2016
Odd article on speciation, since the suggested sympatric speciation doesn't seem to occur in nature either but it is mostly consensus on the allopatric speciation mechanism (i.e.e geographical barrier formation). [ https://en.wikipe...eciation ]

In any case, there wouldn't be one single environment on Earth even in the absence of life. So the suggestion of "one species" seems odd too.

Here may lie the source of the confusion: "a team of physicists has developed a theoretical and experimental model of evolution". Physicists wouldn't necessarily know the biology of speciation.

This is more of a suggestion of an analogy of Darwinian evolution in a toy model (with a later evolved protein) of early populations of nucleotide strands.

Nov 10, 2016
" sexual differentiation was there right from the start".

No, it wasn't, since that evolved in eukaryotes only, quite late and in a relatively small clade of organisms. This is seen in the fossil record in geology as well as in organisms, the latter has enabled us to finally observe the universal common ancestor: "
The physiology and habitat of the last universal common ancestor", Weiss et al, Nature Microbiology 1 (2016).

The rest of your ideas of biology is erroneous too. For instance, nothing is 'created', and the description (theory) of the theory obviously does not need to describe emergence of the first cellular population anymore than our theories of gravity need to describe the emergence of mass, many examples of evolution has been *observed* (seen by scientists based on "eye witness accounts" of geology, say).

We know all of this, and it is because it is science, not the mythology you think it is. Ask your nation's universities about it!

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