Evolution of reproductive strategies of the human and great apes

为了弄清楚人类和类人猿生殖策略的模式，我们试图估计这些物种的精子产量，并比较睾丸的组织学方面。通过尸检或活检获得人(N=7)、大猩猩(10)、黑猩猩(11)、猩猩(7)的睾丸标本，用光学显微镜观察。结果表明，大多数样本在人类(6/7)、黑猩猩(10/11)、猩猩(7/7)中检测到精子发生，而大猩猩(4/10)在少数个体中检测到精子发生。然而，类人猿的这些值与人类的值没有明显的不同。人的间质组织疏松稀少。间质细胞在大猩猩中相当密集，在黑猩猩中相当少，在其他两种动物中居中。各种间生精小管直径和间质生精小管比例均无显著差异。与黑猩猩和猩猩相比，人类生精小管(TLT)的平均估计总长度显著缩短。人类的每管精子数和成熟精子细胞数(CN)均少于黑猩猩。这些物种的平均精子发生指数(SI=TLT×Cn)有显著差异，即人类的精子发生指数低于黑猩猩和猩猩，但高于大猩猩。因此，我们估计黑猩猩、猩猩和大猩猩的精子产量通常分别是人类的60倍、4倍和1/4。

To make clear the pattern of reproductive strategies in the human and great apes, we attempted to estimate sperm production in these species and to compare histological aspects of testes. We obtained testicular preparations of the human (N=7), gorilla (10), chimpanzee (11), orangutan (7) by autopsy or biopsy, and observed them using light microscopes. As the results, spermatogenesis was detected in most samples in humans (6/7), chimpanzees (10/11), orangutans (7/7), but in few individuals in gorillas (4/10). However, the values in great apes were not significantly different from that in the human. The interstitial tissue of the human was loose and scarce. Leydig cells were quite dense in gorillas and quite few in chimpanzees, and intermediate in the other two species. There were not significant differences in diameters of seminiferous tubules nor proportions of seminiferous tubules in the interstitial tissue in all species. The mean estimated total length of seminiferous tubules (TLT) in humans was significantly short, compared with that in chimpanzees and orangutans. The sperm and mature spermatid count per tubule (CN) of humans was less than chimpanzees. The mean spermatogenetic index, calculated as SI=TLT × CN in these species was significantly different from each other, namely that in humans was less than chimpanzees and orangutans, but more than gorillas. Thus, we estimated that a chimpanzee, orangutan, gorilla usually produce 60 times, 4 times and 1/4 time sperm than humans, respectively.