The universal ancestor at the root of the species tree of life depicts a population of organisms with a surprising degree of complexity, posessing genomes and translation systems much like that of microbial life today. As the first life forms were most likely to have been simple replicators, considerable evolutionary change must have taken place prior to the last universal common ancestor. It is often assumed that the lack of earlier branches on the tree of life is due to a prevalence of random horizontal gene transfer that obscured the delineations between lineages and hindered their divergence. Therefore, principles of microbial evolution and ecology may give us some insight into these early stages in the history of life. Here, we synthesize the current understanding of organismal and genome evolution from the perspective of microbial ecology and apply these evolutionary principles to the earliest stages of life on Earth. We focus especially on broad evolutionary modes pertaining to horizontal gene transfer, pangenome structure, and microbial mat communities.
Scholars and the public conceive of extraterrestrial life through the lens of life as we know it on Earth. However, assumptions based on centuries of study around heredity and evolution on Earth may not apply to life truly independent forms of life, and some perspectives accepted or ruled out in the nineteenth century may need to be re-evaluated for life outside of Earth. In honor of the 200th birthday of Mendel, and to provide raw material for the creativity of storytellers, filmmakers, and the public, this thought experiment essay revisits a handful of classic concepts and approaches, as well as some unusual forms of life on Earth, to posit whether different types of genetics and evolution may exist in truly independent extraterrestrial forms. While fundamental evolutionary processes like natural selection and genetic drift are likely to still apply at least similarly in independent life forms, inheritance may be quite radically different from that envisioned by Mendel and others since.
more » « less- Award ID(s):
- 2019789
- NSF-PAR ID:
- 10372862
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Evolution: Education and Outreach
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 1936-6426
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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