More about how evolution works: multicellularity (Evolution)

by David Turell , Sunday, October 30, 2016, 22:35 (2732 days ago) @ dhw

dhw: ... but I have said over and over again that the two purposes “related to evolution” that are clear to me are survival and improvement.

And I have emphasized a drive to complexity as the main force in evolution. This article from MIT professors agrees:

http://www.mdpi.com/2075-1729/6/3/25/htm

Abstract: "Life on Earth provides a unique biological record from single-cell microbes to technologically intelligent life forms. Our evolution is marked by several major steps or innovations along a path of increasing complexity from microbes to space-faring humans. Here we identify various major key innovations, and use an analytical toolset consisting of a set of models to analyse how likely each key innovation is to occur. Our conclusion is that once the origin of life is accomplished, most of the key innovations can occur rather readily. The conclusion for other worlds is that if the origin of life can occur rather easily, we should live in a cosmic zoo, On the other hand, if the origin of life is rare, then we might live in a rather empty universe.

***

" In this paper, we analyse the transitions or key innovations within a theoretical framework that allows us to ask whether the evolution of a technology-using species on Earth is an extremely unlikely event, or whether complex, smart and potentially technological beings are highly likely to evolve on an habitable planet in the time available to it...No evidence of technologically advanced life other than human life has been found, which suggests that such technologically advanced life occurs only on a minor fraction of all habitable planets.

"Our argument rather is that the evolution of complex life is likely. This rests on two arguments. The first is that the functions found in complex organisms have evolved multiple times, an argument we will elaborate in the bulk of this paper. The second is what Gould calls “Diffusion from the Wall”. There is a limit of complexity below which life cannot function... From that simple Last Common Ancestor (LCA), life can evolve genetic, morphological, developmental or behavioural complexity in one of three directions. It can become simpler, it can remain the same, or it can become more complex. If the LCA was a “minimal cell” then it cannot become simpler. However it can become more complex. Such more complex life can also evolve to become simpler or more complex. With time, the most complex life (however complexity is defined) is therefore likely to become more complex. While evolution of simpler forms from complex ones is common, and while the “average complexity” of the biosphere might be unchanged (if it is meaningful at all), the most complex organisms are likely to be more complex.

***

"Our argument rather is that the evolution of complex life is likely. This rests on two arguments. The first is that the functions found in complex organisms have evolved multiple times, an argument we will elaborate in the bulk of this paper. The second is what Gould calls “Diffusion from the Wall”. There is a limit of complexity below which life cannot function (see e.g., [15,16]). It seems plausible that life started as a simple organism, close to this “wall” of minimum complexity. From that simple Last Common Ancestor (LCA), life can evolve genetic, morphological, developmental or behavioural complexity in one of three directions. It can become simpler, it can remain the same, or it can become more complex. If the LCA was a “minimal cell” then it cannot become simpler. However it can become more complex. Such more complex life can also evolve to become simpler or more complex. With time, the most complex life (however complexity is defined) is therefore likely to become more complex. While evolution of simpler forms from complex ones is common, and while the “average complexity” of the biosphere might be unchanged (if it is meaningful at all), the most complex organisms are likely to be more complex.

"Our hypothesis is that the evolution of complex life is highly likely in any stable, sufficiently extensive environment where there is life. By “complex life” we are specifically interested in obligate multicellular life-forms, particularly members of the kingdoms Plantae (plants), Fungi, and Animalia (animals). If the Great Filter is at the origin of life, we live in a relatively empty universe, but if the origin of life is common, we live in a Cosmic Zoo where such complex life is abundant.

***

" All terrestrial life shares the same underlying biochemistry: is this because this biochemistry was the first to appear that our biochemistry is the best fitted (and so independent origins of life converged on it), or that it is the frozen result of an extremely unlikely event.

***

".. we examined the key innovations of life on Earth, and tested them for multiple occurrences... we find that, with the exception of the origin of life and the origin of technological intelligence, we can favour the Critical Path model or the Many Paths model in most cases. The origin of oxygenesis, may be a Many Paths process, and we favour that interpretation, but may also be Random Walk events. This implies that in any world where life has arisen and sufficient energy flux exists, we are confident that we will find complex, animal-like life."

Comment: Extremly long article in which they give many examples of why they think complexity is inevitable. They do not explain the origin of life or consciousness.