Given the complexity of most organisms—sophisticated embryogenesis, differentiation of multiple tissue types, intricate coordination among millions of cells—the emergence of multicellularity was ostensibly a major evolutionary leap. Indeed, most biologists consider it one of the most significant transitions in the evolutionary history of Earth’s inhabitants. But single-celled organisms have stuck together or assembled to spawn multicellular descendants more than two dozen times, suggesting that maybe it’s not such a big leap after all.
1 “These genes that we previously thought were associated with complex multicellular animals really have to do with basic multicellular functions—to get the simplest multicellular animals, you have to have these genes present,” says Srivastava, who coauthored the analysis.
As some of the most ancient animals, sponges can provide information regarding the evolution of the metazoan lineage, but for true insights about the origin of multicellularity, scientists must look even further back on the evolutionary tree. Choanoflagellates, ...
