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How Single Cells Became One Body (Experiments Show How)

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How did cells that lived alone become one body? This video follows one chain of causes, from yeast that fail to let go after dividing, to predators, shared food, specialised cells and cells that signal, ending with the large Ediacaran fossils, from about 575 million years ago. Experiments with yeast and green algae show how fast the early steps can happen; the questions that remain open get one line each. Illustrations are schematic and AI-generated; check the facts before relying on them. Sources: Ratcliff et al. 2012 and 2015; Koschwanez et al. 2013; Boraas et al. 1998; Herron et al. 2019; Bozdag et al. 2023; Kirk 2005; King et al. 2008; Alegado et al. 2012; Brunet et al. 2019; Bobrovskiy et al. 2018; Noble et al. 2015; dos Reis et al. 2015 (full list in references.md). Made with Eureka, a Nebulytic product.

The question

You are trillions of cells that cooperate so completely that you feel like one person. How did cells that once lived alone ever give up living alone, and become one body?

Chapters

  • 0:00One cell, one body: the question
  • 0:43Why daughter cells stay together
  • 1:31Safety in size: predators
  • 2:18Feeding together, and the size race
  • 3:21When a group becomes the unit
  • 4:09Sharing the work: soma and germ
  • 5:13Cells that talk
  • 6:06Becoming one individual
  • 6:46The first animals and the Ediacaran
  • 7:40The story in one line

Sources

  1. Boraas, M.E., Seale, D.B., Boxhorn, J.E. (1998). Phagotrophy by a flagellate selects for colonial prey: a possible origin of multicellularity. Evolutionary Ecology 12:153-164. (read via secondary summaries)
  2. Ratcliff, W.C., Denison, R.F., Borrello, M., Travisano, M. (2012). Experimental evolution of multicellularity. PNAS 109(5):1595-1600. doi 10.1073/pnas.1115323109
  3. Ratcliff, W.C., et al. (2015). Origins of multicellular evolvability in snowflake yeast. Nature Communications 6:6102.
  4. Koschwanez, J.H., Foster, K.R., Murray, A.W. (2013). Improved use of a public good selects for the evolution of undifferentiated multicellularity. eLife 2:e00367.
  5. Herron, M.D., et al. (2019). De novo origins of multicellularity in response to predation. Scientific Reports 9:2328. doi 10.1038/s41598-019-39558-8
  6. Bozdag, G.O., et al. (2023). De novo evolution of macroscopic multicellularity. Nature 617. doi 10.1038/s41586-023-06052-1
  7. Bozdag, G.O., Libby, E., Pineau, R., Reinhard, C.T., Ratcliff, W.C. (2021). Oxygen suppression of macroscopic multicellularity. Nature Communications (title and details to be verified by author).
  8. Kirk, D.L. (2005). A twelve-step program for evolving multicellularity and a division of labor. BioEssays 27:299-310.
  9. Grochau-Wright, Z.I., et al. (2017). Genetic basis for soma is present in undifferentiated volvocine green algae. Journal of Evolutionary Biology.
  10. Herron, M.D., Hackett, J.D., Aylward, F.O., Michod, R.E. (2009). Triassic origin and early radiation of multicellular volvocine algae. PNAS (read via secondary copy).
  11. Koufopanou, V. (1994). The evolution of soma in the Volvocales. American Naturalist 143 (cited via later reviews; original not read; to be verified by author).
  12. Signalling and the animal toolkit
  13. King, N., et al. (2008). The genome of the choanoflagellate Monosiga brevicollis and the origin of metazoans. Nature 451:783-788. doi 10.1038/nature06617
  14. Alegado, R.A., et al. (2012). A bacterial sulfonolipid triggers multicellular development in the closest living relatives of animals. eLife 1:e00013.
  15. Woznica, A., et al. (2016). Bacterial lipids activate, synergize, and inhibit a developmental switch in choanoflagellates. PNAS (to be verified by author).
  16. Brunet, T., et al. (2019). Light-regulated collective contractility in a multicellular choanoflagellate. Science 366(6463):326-334. doi 10.1126/science.aay2346
  17. Sebe-Pedros, A., et al. (2013). Capsaspora adhesion and signalling toolkit. Nature Communications (secondary reading; details to be verified by author).
  18. Bobrovskiy, I., et al. (2018). Ancient steroids establish the Ediacaran fossil Dickinsonia as one of the earliest animals. Science 361(6408):1246-1249. doi 10.1126/science.aat7228
  19. Noble, S.R., et al. (2015). U-Pb dating of the Charnian Supergroup, Charnwood Forest. GSA Bulletin 127:250-265 (Charnia holotype horizons 561.9 +/- 0.9 Ma). The Drook (575 Ma) and Mistaken Point (565 Ma) ages come from other dating papers: to be verified by author.
  20. Dunn, F.S., et al. (2021). Charnia and the origin of animals; Ediacaran morphology and phylogeny (PMC8302126; exact title to be verified by author).
  21. Yuan, X., et al. (2011). The Lantian biota. Nature (older macrofossils, South China; title to be verified by author).
  22. dos Reis, M., et al. (2015). Uncertainty in the timing of origin of animals and the limits of precision in molecular timescales. Current Biology 25(22):2939-2950.
  23. International Commission on Stratigraphy: base of the Cambrian 538.8 Ma.
  24. Evans, S.D., Gehling, J.G., Droser, M.L. (2019). Slime travelers: early evidence of animal mobility and feeding in an organism of the Ediacara biota. Geobiology (title to be verified by author).
  25. Gehling, J.G., Runnegar, B.N., Droser, M.L. (2014). Scratch traces of large Ediacara bilaterian animals. Journal of Paleontology 88.
  26. Counter-argument that Kimberichnus scratches are frost needles: secondary source only, citation to be verified by author.
  27. Grosberg, R.K., Strathmann, R.R. (2007). The evolution of multicellularity: a minor major transition? Annual Review of Ecology, Evolution, and Systematics 38 (via Herron's chapter; pages to be verified by author).
  28. Bianconi, E., et al. (2013). An estimation of the number of cells in the human body. Annals of Human Biology 40.
  29. Sender, R., Fuchs, S., Milo, R. (2016). Revised estimates for the number of human and bacteria cells in the body. PLoS Biology 14(8):e1002533.
  30. Brunet, T., King, N. (2017). The origin of animal multicellularity and cell differentiation. Developmental Cell 43 (review; PMC6089241).
#multicellularity#evolutionofmulticellularity#snowflakeyeast#originofanimals#Volvox#choanoflagellates#Ediacaran#Dickinsonia#experimentalevolution#divisionoflabour#howcellsbecamebodies#evolutionexplained

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