This paper will suggest that the Down syndrome phenotype would have been well suited, physiologically, for a deprived environment and that it may represent a predictive, adaptive response to severe maternal deprivation. A trisomy of the 21st chromosome, prior to, or at conception is responsible for Down syndrome and is known to increase in incidence with advanced maternal age. One out of 11 mothers over the age of 50 conceives a Down syndrome baby, compared to one in one thousand at age 30. This article emphasizes that an older mother is more likely to die before she is able to provide the parental investment necessary to produce an ecologically self-sufficient offspring. Prolonged maternal investment is known to be essential for hunter-gatherers to master the skill intensive food procurement techniques that they will need in order to become independent of their mothers. Because Down syndrome individuals are much more likely to be born to older mothers, they must have been routinely deprived of maternal investment in the human environment of evolutionary adaptedness. This consistent paring of maternal deprivation to trisomy 21 conceptions, over time, may have caused natural selection to favor genes responsible for the energy conserving traits seen in modern day Down syndrome. These traits include muscle hypotonia, decreased cerebral metabolism, decreased hippocampal volume, a strong propensity for obesity and growth hormone and thyroid hormone paucity. Such a "thrifty phenotype" may have allowed Down syndrome individuals to become independent of their mothers at a far earlier age and allowed them to forgo the skill intensive ecological niche that non-trisomic humans are phenotypically suited for in order to take up a less cognitively and physically rigorous one.

译文

:本文将表明,唐氏综合症的表型在生理上非常适合于匮乏的环境,并且它可能代表对严重母体剥夺的预测性,适应性反应。第21号染色体的三体性在受孕之前或受孕时与唐氏综合症有关,并且已知随着高龄产妇的发生率增加。 50岁以上的11名母亲中有1名怀有唐氏综合症婴儿,而30岁时则为千分之一。本文强调,年龄较大的母亲在能够提供生产所需的父母投资之前更容易死亡。一个生态上自给自足的后代。众所周知,延长产妇投资对于猎人/采集者掌握他们需要的技能密集型食品采购技术以使其独立于母亲是必不可少的。因为唐氏综合症的个体更有可能是年长的母亲所生,所以他们必须被例行剥夺了对适应进化的人类环境的母体投资。随着时间的推移,这种对母体剥夺与21三体性观念的一致削减可能导致自然选择偏爱负责现代唐氏综合症中所见的节能特性的基因。这些特征包括肌肉张力减退,大脑代谢减少,海马体积减少,肥胖和生长激素及甲状腺激素缺乏的强烈倾向。这种“节俭的表型”可能使唐氏综合症患者在很早的年龄就变得独立于母亲,并允许他们放弃非三态性人类在表型上适合的技能密集型生态位,从而减少了认知能力。和身体上严谨的。

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