Major transitions in the history of life

Published on March 31, 2016   26 min

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NEIL BLACKSTONE: The title of this lecture is "Major Transitions in the History of Life", and I am Neil Blackstone at Northern Illinois University.
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When we think of the vast sweep of geological time and the massive changes that life on Earth and Earth itself have undergone, it seems impossible that anything about the history of life could exhibit a simple repeating pattern. Yet as remarkable as this may seem, it may also be the case.
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Indeed, the history of life consists of a series of major transitions in which lower-level biological units cooperatively banded together to form higher-level biological units. First groups of molecules, then molecules within simple cells, then simple cells within complex cells, complex cells within multicellular organisms, and even in some cases, multicellular organisms within societies. In the process of these transitions, life became increasingly complex. While there is the simplicity in the repeating pattern, these major transitions themselves were not necessarily simple. In fact, they were perhaps the greatest achievements of organic evolution. In each case, the major obstacle impeding the transition was evolutionary conflict. As lower-level units band together, conflicts arise. Some units free ride using group resources without contributing their fair share. These conflicts must be mediated if a higher-level unit is to emerge.
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Mechanisms of conflict mediation involve a huge variety of biological features. While these mechanisms were no doubt difficult to evolve, there remains a conceptual simplicity in the nature of conflict mediation. Rick Michod points out that mechanisms of conflict mediation in biology typically decrease the variation of the lower-level units, thus decreasing the likelihood that a selfish lower-level unit will evolve. Or increase the variation among the higher-level units, thus increasing the likelihood that a cooperative group will be favored by natural selection. Much of the history of life is the story of the derivation of these mechanisms of conflict mediation. In some sense, much of life is like a bad marriage or maybe a good marriage, lots of fighting among the lower-level units as 'who should do the dishes and take out the trash' until mechanisms to mediate these conflicts evolve and the higher-level unit emerges.
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Major transitions in the history of life

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