Pomiankowski A
Galton Laboratory, Department of Biology, University College London, London NW1 2HE, UK.
Novartis Found Symp. 2000;233:228-37; discussion 237-42. doi: 10.1002/0470870850.ch14.
It has been suggested that complex traits, like intelligence, have low heritabilities. This hypothesis stems from the idea that strong selection for higher intelligence has led to the fixation of genetic variation for this trait. The same hypothesis has been framed for complex sexual ornaments used in courtship display. These traits are also subject to directional selection, in this case caused by sexual selection. However, contrary to the hypothesis, comparative data shows that sexual ornaments have higher additive genetic variation than similar non-sexual traits. It appears that the number of variable genes and the effect per genetic locus have increased for sexual ornaments. Theory suggests this is due to selection for extreme phenotypes resulting in condition-dependent expression of sexual traits. Experimental work on the stalk-eyed fly, Cyrtodiopsis dalmanni, confirms that the male sexual trait (exaggerated eyespan) is more sensitive to environmental conditions than other non-sexual traits (wing dimensions and female eyespan). This environmental sensitivity has a genetic basis and environmental stress enhances genetic differences. It is likely that genetic variation in intelligence is maintained in a similar fashion.
有人认为，像智力这样的复杂性状具有较低的遗传力。这一假设源于这样一种观点，即对更高智力的强烈选择导致了该性状遗传变异的固定。同样的假设也适用于求偶展示中使用的复杂性装饰。这些性状也受到定向选择，在这种情况下是由性选择引起的。然而，与该假设相反，比较数据表明，性装饰比类似的非性性状具有更高的加性遗传变异。似乎性装饰的可变基因数量和每个基因座的效应都增加了。理论表明，这是由于对极端表型的选择导致性性状的条件依赖性表达。对达尔曼氏突眼蝇的实验研究证实，雄性性性状（夸张的眼距）比其他非性性状（翅尺寸和雌性眼距）对环境条件更敏感。这种环境敏感性有遗传基础，环境压力会增强遗传差异。智力的遗传变异可能以类似的方式得以维持。
