I think I can state with some confidence that the scientists now have decided that comb jellies are humankind’s ancient ancestors. We can look to these blob-like creatures as the start of animal life and therefore of human life.
A study as long ago as 2013 decided that comb jellies evolved before sponges (‘Genome reveals comb jellies’ ancient origin’). And therefore, they beat sponges into being the originator of current animal and human life. It appears that among scientists there was a competition as to whether it was the sponges or the comb jellies who were the origin of humankind. The comb jellies have won that battle it appears mainly because they have muscles and neurons (nerve cells) while sponges do not.
It is therefore more likely or should I say common sense dictates that they then evolved over billions of years into humankind.
A more recent study has shed some light on this. They try to answer the question of which came first, the sea-sponge or the comb jelly?
Sponges are sedentary and simple sea creatures while comb jellies are gelatinous creatures which swim through the oceans.
They evolved more than 500 million years ago and the researchers say that “one of them became the first type of animal to diverge away from its ancestral lineage and form its own branch on the evolutionary tree”. The quote comes from Rhys Blakely, the science correspondent at The Times in an article dated May 18, 2023 (thanks).
The quoted statement does not tell me anything about the ancestral lineage (correct: they were unicellular organisms – see below). I would like to know what came before the comb jelly but perhaps that isn’t important.
It is said that we can now build a clearer picture of what the ancestor of all animals looked like. As mentioned, the assumption is that the originators of mankind had muscles and nerves just as we have.
Dr. Darrin Schultz of the University of Vienna who led the study said:
The last ancestor of all animals, which probably existed around 700 million years ago or longer, also had neurons and muscles.
Until this research many scientists believed or assumed that sponges had been the first creatures to branch off from this ancient lineage and then evolved to create animals and the human animal. But the assumption was based on the fact that this ancient ancestor lacked neurons and muscles. It was also an assumption which is based on the theory that sponges evolved to where they developed muscles and neurons. This theory has now it seems been ruled out.
The scientists’ analysis of chromosomes revealed “key similarities between the chromosomes of comb jellies and those of primitive unicellular organisms which shared a common ancestor around a billion years ago.”
They say that in all the other animal lineages including the sea sponges, the 14 groups of genes have been reorganised and now form seven different groups. They say that this could only have happened after the comb jellies had split away. And this establishes that the comb jellies came first as I understand the research and therefore, they are the originators of human life on planet Earth today.