[Taxacom] human-specific loss of regulatory DNA
Richard.Zander at mobot.org
Tue Mar 15 12:01:50 CDT 2011
John's point is important and theory-based. Parsimony analysis becomes nonsense when the ancestral taxon theoretically has static expressed traits and theoretically gave rise to more than one lineage, and thus longer trees must be accepted, theoretically. The parsimony or Bayesian "discovery process" fails in light of constraints offered by theory.
I encourage him to submit this to Nature. Probably needs citation of papers.
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Richard H. Zander
Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USA
Web sites: http://www.mobot.org/plantscience/resbot/ and http://www.mobot.org/plantscience/bfna/bfnamenu.htm
Modern Evolutionary Systematics Web site: http://www.mobot.org/plantscience/resbot/21EvSy.htm
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of John Grehan
Sent: Tuesday, March 15, 2011 10:56 AM
Subject: [Taxacom] human-specific loss of regulatory DNA
Due to the kind response by several on this list I was able to read over a recent paper in Nature on human-specific loss of regulatory DNA and the evolution of human-specific traits. I have drafted a letter to Nature as a bit of a long shot, and although this is less about systematics, there may be people on this list who could give me feed back (if there is anything so deserving) before I submit, particularly as it involves a specialized area of developmental genetics which is a bit of a different field to that of simple DNA sequence comparisons in systematics. I have not included citations yet, but the draft text is below. I am interested to know if I have made any errors of fact.
Human-specific loss of regularity DNA associated with the loss of penile spines (resulting in prolonged copulation) is seen by McLean et al
(2011) to fit with an adaptive suite associated with pair bonding and increased paternal care that also includes reduction of male canines, moderate sized testes with low sperm motility, concealed ovulation, and permanently enlarged mammary glands. But the absence of penile spines is also characteristic of gorillas and orangutans which both have developed male canines and lack human pair bonding patterns and paternal care.
Orangutans are also more like humans than African apes in having concealed ovulation, prolonged copulation that is similar in duration to humans, and moderate sized testes (relative to body size). These similarities are correlated with a large suite of unique morphogenetic similarities shared between humans and orangutans that suggest evolution from a last common ancestor that did not include the chimpanzee and need not, therefore, to have evolved separately within hominids because of evolution in pair bonding and paternal care.
In view of the contrasting evidence between molecular sequence evidence for the chimpanzee and morphogenetic evidence for the orangutans, the evolution of human characteristics cannot be assumed to have evolved within hominids, particularly if they are also present in orangutans.
Future work on DNA deletions such as those correlated with the loss of penile spines may benefit from a detailed comparison to see whether these deletions are also present in orangutans and gorillas and whether such deletions are homologues, if that is possible where sequence alignment is used to create homology.
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