Evolution at Work

There were a couple of great stories in the news recently that illustrate how evolution works in practice. The first is a study of the evolution of electrocytes in electric eels.

The genome of the electric eel (pictured) has been sequenced for the first time. The results of a new study indicate that, despite millions of years of evolution, independent lineages of eel developed electric organs in a similar way. Worldwide, there are hundreds of species of electric fish, in six broad lineages

Here are some aspects highlighted by the findings:

*Evolution is not as “random” as you might think

Based on the DNA sequence data, it appears that electrocytes evolved independently at least six times. This convergent evolution show that there are “attractors” in the space of all possible creatures, and the development of species, while based on random mutations, is not completely random.

*Evolution works with what is available

In these species, muscle cells, which already use ion channels to create electric signals to control contractions, were re-purposed into specialized electrocytes. Instead of starting from scratch, evolution tinkers with what already works and finds new ways to use it.

*Evolution knows more physics than you

All organisms need to follow the laws of physics, but evolution finds ways to take advantage of this rules. In electronic devices, stacking batteries in series causes their voltages to be added. In electric eels, stacks of electrocytes can reach 600 volts.

*Gradual improvement is possible

Although not discussed at length in this article, scientists think that electrocytes originality evolved to help eels navigate in murky water. This would not require large voltages, so it would still be advantageous compared with eels without this ability. Later, the voltages could be increased to incapacitate prey.

 

The other article sheds light on the ability of people in Tibet to live at such high altitudes:

       

“Past research has concluded that a particular gene helps people live in the thin air of the Tibetan plateau. Now scientists report that the Tibetan version of that gene is found in DNA from Denisovans, a poorly understood human relative more closely related to Neanderthals than modern people.” 

Most people have a variant of the gene that responds to the thin air at high altitudes by increasing the production of red blood cells. This causes health problems due to “thick blood.” In contrast, Tibetans have a version of the gene that does not make so many red blood cells.

 

*There are many ways for genes to get around

It is clear that the ancestors of modern humans mated with Denisovans (and Neanderthals) before presumably driving them to extinction. The boundary between species is not as stark as we usually think.

*Gene variants can be rare, until there are not

In all likelihood, this gene variant conferred little to no advantage to Denisovans. In fact, for people not living in the mountains, it was probably slightly detrimental. Therefore, was probably rare in humans until some decided to start living in the Himalayan region. At that point, being able to withstand the effects of the high altitude was a huge bonus.  Then, this gene variant spread widely. Again, evolution works with what is already lying around.

 

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Author: lnemzer

Assistant Professor Nova Southeastern University

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