In the experiments of American scientists, it took baker's yeast only 60 days to start living in communities, where all members of the group are united by a common good and are ready to sacrifice themselves to comradely interests.
It is believed that fundamental evolutionary changes, such as the transition from single-celled to multicellularity, took an incredibly long time - millions (if not billions) of years. Evolution really does not like haste, and the more global the changes, the longer it takes to prepare for them.
However, now there is reason to doubt such a slow-wittedness of evolution - at least with regard to the emergence of multicellularity. In the experiments of scientists from the University of Minnesota (USA), unicellular organisms turned into multicellular organisms in just a few months.
Usual baker's yeast was taken as a model object. These unicellular fungi reproduce by budding: when the mother cell grows to a certain size, the smaller daughter one buds from it and goes into free swimming. According to scientists, the main problem was not even planning an experiment to turn unicellular yeast into multicellular yeast, but at least a mental assumption that this process could be carried out in the foreseeable future. It is generally accepted that multicellularity has appeared in the history of life on Earth at least 25 times, but the circumstances of its appearance are hidden from us. We can only guess about the conditions that made individual cells seek help from each other.
William Ratcliffe and his colleagues chose the gravitational field as the driving force. They hypothesized that gravity was the factor that favored the emergence of multicellular organisms. It is obvious that the cell complexes that floated in the prehistoric ocean settled to the bottom faster than single cells. Yeast can also stick to each other, forming large clusters, and in the experiment, the largest clusters settled to the bottom faster than their smaller "cousins", not to mention single cells. Time after time, the researchers selected the clusters that settled to the bottom in the first place, cultured them again, and re-selected the largest samples.
Of course, an ordinary clump of stuck together cells is not yet a multicellular organism. But here scientists were able to show that the clusters of yeast with which they worked consisted of genetically related cells, that is, all members of the group were descendants of the same parent. The yeast multiplied, but the daughter cells remained adhered to the parent cells. And, more importantly, the cell clusters in the experiments began to behave like single organisms. They had a juvenile stage during which they grew up and an adult stage, when the cluster multiplied, dividing into larger and smaller parts. It was like the budding of a small daughter cell from the parent, only here everything happened at the level of a whole cluster. In this case, some cells sacrificed themselves: they died in order to allow the child and parent clusters to disperse. That is, the cells turned out to be not just a gathering, where everyone was for himself, but a community whose members collaborated for the common good. The dead cells benefited a whole cluster, which needed to be divided for successful life. By dying, they enabled the entire community to survive and create more descendants.
The most curious thing is that the experiment took 60 days. According to scientists, they ended up with individual clusters of yeast cells that lived and died as a whole. All together indicated that during the experiment the yeast managed to find a way towards multicellularity.
Until now, scientists have pointed out that multicellular organisms could have different advantages over unicellular ones. But very, very few studies show direct "assembly" of a multicellular organism, as it could have happened billions of years ago. The researchers are preparing to publish their results in the journal PNAS.
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After reading all of this, you must be thinking: it's incredible that multicellular organisms have appeared only a few times in the course of evolution. Indeed, since this did not take so much time, there could have been immeasurably more such attempts. In the future, the authors are going to repeat their experiments on other modern multicellular organisms. The fact is that the current yeast descended from multicellular ancestors, and some kind of memory of this could remain with them. Therefore, scientists want to force other organisms to multicellularity, like Chlamydomonas algae, which did not have a multicellular past.