Momentous transition to multicellular life may not have been so hard after all


EXCERPT: Billions of years ago, life crossed a threshold. Single cells started to band together, and a world of formless, unicellular life was on course to evolve into the riot of shapes and functions of multicellular life today, from ants to pear trees to people. It's a transition as momentous as any in the history of life, and until recently we had no idea how it happened.

The gulf between unicellular and multicellular life seems almost unbridgeable. A single cell's existence is simple and limited. Like hermits, microbes need only be concerned with feeding themselves; neither coordination nor cooperation with others is necessary, though some microbes occasionally join forces. In contrast, cells in a multicellular organism, from the four cells in some algae to the 37 trillion in a human, give up their independence to stick together tenaciously; they take on specialized functions, and they curtail their own reproduction for the greater good, growing only as much as they need to fulfill their functions. When they rebel, cancer can break out.

Multicellularity brings new capabilities. Animals, for example, gain mobility for seeking better habitat, eluding predators, and chasing down prey. Plants can probe deep into the soil for water and nutrients; they can also grow toward sunny spots to maximize photosynthesis. Fungi build massive reproductive structures to spread their spores. But for all of multicellularity's benefits, says László Nagy, an evolutionary biologist at the Biological Research Centre of the Hungarian Academy of Sciences in Szeged, it has traditionally "been viewed as a major transition with large genetic hurdles to it."

Now, Nagy and other researchers are learning it may not have been so difficult after all. The evidence comes from multiple directions. The evolutionary histories of some groups of organisms record repeated transitions from single-celled to multicellular forms, suggesting the hurdles could not have been so high. Genetic comparisons between simple multicellular organisms and their single-celled relatives have revealed that much of the molecular equipment needed for cells to band together and coordinate their activities may have been in place well before multicellularity evolved. And clever experiments have shown that in the test tube, single-celled life can evolve the beginnings of multicellularity in just a few hundred generations—an evolutionary instant.

Evolutionary biologists still debate what drove simple aggregates of cells to become more and more complex, leading to the wondrous diversity of life today. But embarking on that road no longer seems so daunting. "We are beginning to get a sense of how it might have occurred," says Ben Kerr, an evolutionary biologist at the University of Washington in Seattle. "You take what seems to be a major step in evolution and make it a series of minor steps."

Hints of multicellularity date back 3 billion years...

That's nothing compared to abiogenesis.
Note to reader: This in no way contradicts the existence of God. In fact, it supports it. As you can see, sticking together for the greater good works to curb failure to survive.

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