From Simple To Complex

The switch from single-celled organisms to ones made up
of many cells has evolved independently more than two dozen times. What can this transition teach us about the origin of complex organisms such as animals and plants?

Sean McCabe

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.

Related Articles

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...

1. M. Srivastava et al., “The Amphimedon queenslandica genome and the evolution of animal complexity,” Nature, 466:720-26, 2010. Free F1000 Evaluation
2. N. King et al., “The genome of the choanoflagellate Monosiga brevicollis and the origin of metazoans,” Nature, 451:783-88, 2008. Free F1000 Evaluation
3. A. Sebé-Pedrós et al., “Ancient origin of the integrin-mediated adhesion and signaling machinery,” PNAS, 107:10142-47, 2010.
4. C.W. Dunn et al., “Broad phylogenomic sampling improves resolution of the animal tree of life,” Nature, 452:745-49, 2008. Free F1000 Evaluation
5. J.M. Cock et al., “The Ectocarpus genome and the independent evolution of multicellularity in brown algae,” Nature, 465:617-21, 2010. Free F1000 Evaluation
6. M.D. Herron et al., “Triassic origin and early radiation of multicellular volvocine algae,” PNAS,106:3254-58. 2009.
7. P. Ferris et al., “Evolution of an expanded sex-determining locus in Volvox,” Science, 328:351-54, 2010.
8. S.R. Fairclough et al., “Multicellular development in a choanoflagellate,” Current Biology, 20:R875-76, 2010.

Interested in reading more?

Magaizne Cover

Become a Member of

Receive full access to digital editions of The Scientist, as well as TS Digest, feature stories, more than 35 years of archives, and much more!
Already a member?