All living beings on Earth have a common ancestor, the creature which created the bottom branch of the tree of life. However, scientists have kept debating the origin of this primordial creature for many years. After intense research, they might have finally found an answer. Our most ancient ancestors are sponges, and not comb jellies like so many other scientists thought.
There are two theories concerning the common ancestor of all creatures
Both sponges and comb jellies are extremely complex animals. The latter, for instance, have a nervous system and a well-functioning digestive system. However, finding out how sponges work might unravel the mystery of all living creatures. Although comb jellies seem more evolved, it turns out this complexity excludes them from the bottom of the evolutionary tree.
The first creature which gave rise to all the other complex life forms needs to be a simpler creature. Although comb jellies share more features with today’s animals, these characteristics had to evolve multiple times until they reached the most primordial form. Therefore, everything started with the sponges.
Statistics indicate sponges as the bottom of the evolutionary tree
Both creatures were placed at the bottom of the tree of life, but at different points in the evolution. This was given by a mixed interpretation of different sets of phylogenetic data. Therefore, one and the same evolutionary tree was analyzed differently, producing more sets of results.
To establish which interpretation was correct, scientists used the method statistical called Posterior Predictive Analysis. Through this method, they looked at all the available models and saw which was closest to reality. Therefore, they noticed the only accurate interpretations placed sponges at the origin.
However, the fight might not be over. There are still plenty of scientists who support the comb jelly hypothesis, and who might not be willing to give up, even if statistics say otherwise. The study which promotes sponges as our common ancestor has been published in the journal Current Biology.
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