Sandel Aaron A, Negrey Jacob D, Arponen Milja, Clark Isabelle R, Clift Jeremy B, Reddy Rachna B, Ivaska Kaisa K
Department of Anthropology, University of Texas at Austin, WCP 4.102, 2201 Speedway Stop C3200, Austin, TX 78712, USA; Primate Ethology and Endocrinology Lab, University of Texas at Austin, 2201 Speedway Stop C3200, Austin, TX 78712, USA.
School of Human Evolution and Social Change, Arizona State University, 900 S. Cady Mall, Tempe, AZ 85281, USA; Department of Pathology/Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27101, USA.
J Hum Evol. 2023 Apr;177:103341. doi: 10.1016/j.jhevol.2023.103341. Epub 2023 Mar 9.
Life history theory addresses how organisms balance development and reproduction. Mammals usually invest considerable energy into growth in infancy, and they do so incrementally less until reaching adult body size, when they shift energy to reproduction. Humans are unusual in having a long adolescence when energy is invested in both reproduction and growth, including rapid skeletal growth around puberty. Although many primates, especially in captivity, experience accelerated growth in mass around puberty, it remains unclear whether this represents skeletal growth. Without data on skeletal growth in nonhuman primates, anthropologists have often assumed the adolescent growth spurt is uniquely human, and hypotheses for its evolution have focused on other uniquely human traits. The lack of data is largely due to methodological difficulties of assessing skeletal growth in wild primates. Here, we use two urinary markers of bone turnover-osteocalcin and collagen-to study skeletal growth in a large, cross-sectional sample of wild chimpanzees (Pan troglodytes) at Ngogo, Kibale National Park, Uganda. For both bone turnover markers, we found a nonlinear effect of age, which was largely driven by males. For male chimpanzees, values for osteocalcin and collagen peaked at age 9.4 years and 10.8 years, respectively, which corresponds to early and middle adolescence. Notably, collagen values increased from 4.5 to 9 years, suggesting faster growth during early adolescence compared to late infancy. Biomarker levels plateaued at 20 years in both sexes, suggesting skeletal growth continues until then. Additional data, notably on females and infants of both sexes, are needed, as are longitudinal samples. However, our cross-sectional analysis suggests an adolescent growth spurt in the skeleton of chimpanzees, especially for males. Biologists should avoid claiming that the adolescent growth spurt is uniquely human, and hypotheses for the patterns of human growth should consider variation in our primate relatives.
生活史理论探讨了生物体如何平衡发育和繁殖。哺乳动物通常在婴儿期投入大量能量用于生长，随着年龄增长，这种投入逐渐减少，直至达到成年体型，此时它们将能量转移到繁殖上。人类的情况较为特殊，在漫长的青春期，能量既用于繁殖，也用于生长，包括青春期前后骨骼的快速生长。尽管许多灵长类动物，尤其是圈养的灵长类动物，在青春期前后体重增长加速，但尚不清楚这是否代表骨骼生长。由于缺乏关于非人类灵长类动物骨骼生长的数据，人类学家常常认为青春期生长突增是人类独有的现象，并且其进化假说也主要围绕其他人类独有的特征展开。数据的缺失很大程度上是由于评估野生灵长类动物骨骼生长存在方法上的困难。在此，我们使用两种骨转换的尿液标志物——骨钙素和胶原蛋白，来研究乌干达基巴莱国家公园恩戈戈地区的一大组野生黑猩猩（黑猩猩属）的骨骼生长情况。对于这两种骨转换标志物，我们发现年龄存在非线性效应，且这种效应在很大程度上由雄性驱动。对于雄性黑猩猩，骨钙素和胶原蛋白的值分别在9.4岁和10.8岁时达到峰值，这分别对应青春期早期和中期。值得注意的是，胶原蛋白的值在4.5岁至9岁之间有所增加，这表明与婴儿晚期相比，青春期早期的生长速度更快。两性的生物标志物水平在20岁时趋于平稳，这表明骨骼生长一直持续到那时。还需要更多数据，特别是关于雌性和两性婴儿的数据，以及纵向样本。然而，我们的横断面分析表明黑猩猩骨骼存在青春期生长突增，尤其是雄性。生物学家应避免声称青春期生长突增是人类独有的现象，关于人类生长模式的假说应考虑我们灵长类亲属的差异。
