Biology:Cosmic ancestry
Cosmic ancestry is a hypothesis of the origin of life on Earth, based on the panspermia views of Fred Hoyle and Chandra Wickramasinghe. Cosmic Ancestry speculates that life, like the universe itself, has no date of origin, and has always existed and can only descend from ancestors at least as highly evolved as itself.[1] Under this belief, life on Earth was delivered from space. This belief stands in stark contrast to the theory accepted by most cosmologists that the age of the universe is roughly 13.8 billion years,[2] and that sufficient evidence is not available to presume whether life exists outside the Earth, let alone the age of that life.
History
Hoyle was a long-standing advocate of strong panspermia. He claimed (with Wickramasinghe) that spectral analysis of interstellar dust indicated that large organic molecules and even bacterial spores occur in space.[3] He also viewed natural selection and mutation as too weak a mechanism to drive evolutionary progress.[4] Moreover, his belief in a quasi-steady state universe allowed him to consider the possibility that life was much older than orthodox cosmology would allow. Whilst Wickramasinghe and Hoyle referred to their ideas as either panspermia or cosmic ancestry [1], the latter term has come to be associated with an expanded hypothesis proposed by Klyce,[citation needed] which incorporates the Gaia hypothesis of James Lovelock.
Proposition
Cosmic ancestry holds that life is neither the product of supernatural creation, nor is it spontaneously generated through abiogenesis, but that it has always existed in the universe. It claims that the evolutionary progression from simpler to more complex organisms utilises pre-existing genetic programs such as whole genes, delivered by horizontal gene transfer.
According to this proposition, higher life forms, including intelligent life, descend ultimately from pre-existing life which was at least as advanced as the descendants. The genetic programs for the evolution of such higher forms may have been delivered to biospheres, such as the Earth's, within viruses or bacteria in the same manner as proposed by other versions of panspermia. The genetic programs may then be installed by known gene transfer mechanisms. Also, according to cosmic ancestry, life initiates Gaian processes that may environmentally alter biospheres.
Cosmic ancestry is opposed to both neo-Darwinism and Intelligent design theories. Its assertions require the universe to be ageless.
To these considerations could be added the ontological argument: life, like the rest of the Universe, exists simply because it can. Since this has presumably always been so, it would follow that both are indeed ageless. As Richard Feynman has said, "Anything that is not forbidden [by physical law] is compulsory".
Hypothesis
Arguments for the possible astral origin of life are summarised in theoretical panspermia. Recent evidence[citation needed] suggests that mechanisms other than random mutation and natural selection could play an important role in evolution - it is now apparent that horizontal gene transfer is much more widespread than previously thought.[citation needed] There are also many instances of genes detected in species that have no known current use for them.[5][6][7] It is claimed that other aspects of evolution which present problems for neo-Darwinism are more easily explained by cosmic ancestry or panspermia, such as life's rapid start on Earth [2], punctuated equilibrium and convergent evolution.[citation needed]
The primary justification for the hypothesis is claimed to be the lack of direct evidence that any natural process can (1) cause life to originate from non-living matter,[citation needed] or (2) compose genetic programs for new evolutionary features.[citation needed] Evidence for speciation, adaptation, variation, and optimization within narrow ranges via natural selection is not disputed.
Criticisms
Postulating that life (and the universe) have always existed is contrary to nearly all contemporary scientific views. The cosmic ancestry hypothesis has been largely ignored by the scientific community. Most biologists regard natural selection as an adequate (although not fully understood) and more plausible explanation for the evolution of life on Earth. Some evidence, such as Hoyle's interpretation of his spectral analysis, is disputed.[citation needed]
If viruses or spores had been found on those heavenly bodies already visited by space probes, the case for extraterrestrial life would be strengthened, but they have not.
See also
References
- ↑ Introduction: More Than Panspermia
- ↑ Bennett, C.L.; Larson, L.; Weiland, J.L.; Jarosk, N.; Hinshaw, N.; Odegard, N.; Smith, K.M.; Hill, R.S. et al. (December 20, 2012). "Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results". The Astrophysical Journal Supplement Series 1212 (2): 5225. doi:10.1088/0067-0049/208/2/20. Bibcode: 2013ApJS..208...20B.
- ↑ F. Hoyle and C. Wickramasinghe. "On the Nature of Interstellar Grains" p 77-90 v 66 Astrophysics and Space Science. 1979
- ↑ F. Hoyle, Mathematics of Evolution p 97-109 ISBN:0-9669934-0-3; Memphis: Acorn Enterprises LLC, 1999
- ↑ Ulrich Technau et al., "Maintenance of ancestral complexity and non-metazoan genes in two basal cnidarians" [abstract], doi:10.1016/j.tig.2005.09.007, p 633-639 v 21, Trend in Genetics, December 2005
- ↑ Raible, F.; Tessmar-Raible, K.; Osoegawa, K.; Wincker, P.; Jubin, C.; Balavoine, G.; Ferrier, D.; Benes, V. et al. (Nov 2005). "Vertebrate-type intron-rich genes in the marine annelid Platynereis dumerilii ". Science 310 (5752): 1325–1326. doi:10.1126/science.1119089. ISSN 0036-8075. PMID 16311335. Bibcode: 2005Sci...310.1325R.
- ↑ Arne Kusserow et al., "Unexpected complexity of the Wnt gene family in a sea anemone", doi:10.1038/nature03158, p 156-160 v 433, Nature, 13 Jan 2005
External links
 |
