Jakarta, CNN Indonesia —
Living beings evolve and generate complexities in his body to adapt to environment. But what if this complexity isn’t needed and evolution goes in reverse?
Evolution has resulted in making living things that were originally simple in shape have very complex features, such as the arms of an octopus that has neurons to the ears of mammals.
However, can evolution go the other way, or in other words reverse evolution, aka regressive evolution; living things lose their complex features and instead return to their simpler forms?
“It is likely that the same trip [dari perubahan evolusioner] would … be reversed in the same way is very unlikely,” said William R. Jeffery, a biologist at the University of Maryland, as quoted LiveScience.
However, Beth Okamura, a life sciences researcher at the Natural History Museum in London, said regressive evolution could occur involving the loss of complex forms that grew from earlier evolution.
One extreme example comes from myxozoans, parasites with very small genomes and very simple anatomy, that is, there is no mouth, nervous system, or gut. Okamura calls the simplest form “essentially a single cell.”
Myxozoans that are classified as single-celled protozoa reveal themselves as highly retarded animals. Okamura explained that these microorganisms evolved from cnidarians, the group that includes jellyfish.
This organism loses many features that are no longer needed in the life of a parasite. Thus, myxozoans appear morphologically to have reverted to a previous evolutionary stage.
“They kind of go back to being single-celled organisms,” says Okamura.
Furthermore, Jeffery emphasized that the process of regressive evolution does not go through the same path as the evolutionary process.
For example, cave-dwelling creatures, which also frequently underwent regressive evolution, lost complex features, such as eyes, that were unnecessary in dark environments. However, losing eyes in cave fish does not mean they have completely disappeared.
On the other hand, the process that previously produced the eye instead stopped midway, leaving behind the eye but covered in skin.
“Things can look like they’re going backwards,” said Jeffery, “But the eyes don’t evolve backwards. They just stop (evolve) forwards.”
This regressive evolution that eliminates complexity in living things can also be accompanied by changes in other things in terms of physiology and biochemistry.
“It’s very easy for people to think of evolution in terms of what you see, what the morphological features are. But there are also many other features that we don’t see at the physiological and biochemical level,” said Okamura.
(lom/lth)
