A new research challenges the previous theory which claimed that the first life form on Earth was a sponge. The study, published in the journal Nature Ecology & Evolution, claims that our first ancestor was actually a marine jelly.
This theory was proposed for the first time in 2008. It claimed that ctenophores, also known as comb jellies, are actually the first live beings on Earth. This proposal has the potential to change the theory of evolution, and faced many opponents among those who supported the sponge theory.
An advanced genetic analysis chose one species over the other
Thus, the researchers from Vanderbilt University and Wisconsin-Madison decided to find out who is right and performed a special genetic analysis to obtain the answer. This analysis brought more results in favor of the jelly as the ancestor of all life on Earth.
They collected extensive genetic samples from many animal species, then they tried to discover what relationships lie between them. With all the information, they tried to put up a family tree. This method proved accurate in 95 percent of the cases. With the remaining 5 percent, the researchers faced great challenges.
Thus, they turned to the analysis of those genes which they found present in all the studied organisms. By looking at these particular genes, they were able to identify what other organisms they resemble the most. The final results showed that the jelly shares genes with more organisms than the sponge. This technique can be described as phylogenetic.
Using the phylogenetic technique to solve many other evolution puzzles
This is quite a widespread technique, as previous studies used it to establish the origin of other species. For instance, scientists looked if crocodiles shared genes with birds or with turtles. In this case, the immediately related species was turtles, and birds were a more distant relative.
Sometimes it happens that one single gene does not act as it should and the whole theory is turned upside down. This happened, for instance, with the origin of flowers or birds. In this case, the genetic sequence varies from one species to another, so researchers cannot say how evolution went.
This is why this phylogenetic technique is useful. It might be used to solve these controversies by accurately finding the closest relative. Thus, scientists will be able to build up family trees for many species and answer the evolution question once and for all.
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