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Sexual Selection Promotes Giraffoid Head-Neck Evolution and Ecological Adaptation


The morphology and inferred ecology of D. xiezhi provide another example for understanding the neck evolution in giraffoids. Fossil giraffoids exhibit a higher degree of diversity in headgear morphology than any other pecoran group; such a diversity, associated with the complex head-neck morphology, likely indicates the intensive sexual combats between males in the evolution of giraffoids. For interspecific relationship, one possible strategy of early giraffoids is that they might have avoided competition with coeval bovids and cervids by taking advantage of other niches in the ecosystem. Giraffa,with its long neck, did not appear until the early Pliocene in savannah areas, when C4 ecosystems started being vastly established. “Necking” combat was likely the primary driving force for giraffes that have evolved a long neck, and high-level browsing was likely a compatible benefit of this evolution. The ecological positioning on the marginal niches promoted the intensive sexual competition, and the fierce sexual combats fostered extreme morphologies to occupy the special niches in giraffoids.


Edited by Boydstun
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  • Charles Darwin wrote this: “All that we can do is to keep steadily in mind that each organic being is striving to increase in a geometrical ratio; that each, at some period of its life, during some season of the year, during each generation, or at intervals, has to struggle for life and to suffer great destruction. When we reflect on this struggle we may console ourselves with the full belief that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply.” (Origin of Species)
  • Charles Darwin wrote this:  "The advancement of the welfare of mankind is a most intricate problem: all ought to refrain from marriage who cannot avoid abject poverty for their children; for poverty is not only a great evil, but tends to its own increase by leading to recklessness in marriage. On the other hand, as Mr. Galton has remarked, if the prudent avoid marriage, whilst the reckless marry, the inferior members tend to supplant the better members of society. Man, like every other animal, has no doubt advanced to his present high condition through a struggle for existence consequent on his rapid multiplication; and if he is to advance still higher, it is to be feared that he must remain subject to a severe struggle. Otherwise he would sink into indolence, and the more gifted men would not be more successful in the battle of life than the less gifted. Hence our natural rate of increase, though leading to many and obvious evils, must not be greatly diminished by any means. There should be open competition for all men; and the most able should not be prevented by laws or customs from succeeding best and rearing the largest number of offspring. (The Descent of Man)
  • Charles Darwin wrote this: "[Y]ou have expressed my inward conviction, though far more vividly and clearly than I could have done, that the Universe is not the result of chance. … Lastly, I could show fight on natural selection having done and doing more for the progress of civilization than you seem inclined to admit. Remember what risk the nations of Europe ran, not so many centuries ago of being overwhelmed by the Turks, and how ridiculous such an idea now is! The more civilized so-called Caucasian races have beaten the Turkish hollow in the struggle for existence. Looking to the world at no very distant date, what an endless number of the lower races will have been eliminated by the higher civilized races throughout the world. (Letter to William Graham, July 3, 1881)
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Posted (edited)

I'd rather the science, not dumbing down and not humanities' social-agendas rattle-talk, LB, for this sector, advances as in root post and in these links. 

Evidence of early evolution of the mammalian middle ear--one of the most important features for all modern mammals.

Between Aquatic and Land Vertebrates

The good social news is that science, the hard sciences, continue to roll back the darkness as ever since Newton and with much educated public interest, including readers at this site, any presumption, wishing, or hollering to the contrary notwithstanding. 

Edited by Boydstun
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