Kramer P A
Department of Anthropology, University of Washington, Seattle, USA.
Am J Phys Anthropol. 1998 Sep;107(1):71-85. doi: 10.1002/(SICI)1096-8644(199809)107:1<71::AID-AJPA6>3.0.CO;2-G.
This article investigates maternal investment in child carrying and presents a method for determining when it is energetically advantageous for a mother to carry her child rather than force her child to walk independently. I calculate maternal and child energy consumption while walking and develop correction factors to facilitate making these energy calculations for young children. In addition, I investigate the effect of maternal burdens in addition to the child and of external nutritional support on energy consumption. Since maternal energy is a finite resource, the "decision" to carry a child or force it to walk independently is especially important. This decision can be predicted from the body mass of the mother and child and the child's age. If the mother provides all of the child's nutrition, then the mother should choose to carry her child only when the energy usage of the mother carrying the child is less than the sum of the energy used when the mother and child walk independently. The critical velocity, when the two expenditures are equal, can then be determined. Several general hypotheses are also addressed. The critical velocity of a 60 kg mother with a 4-year-old child approximately equals the average walking speed of adult humans. For a lighter mother, the critical velocity is reached when her child is 3 years old, while for heavier mother this point is not reached until her child is 6 years old. The effect of burdens in addition to the child's mass is minimal. Nutritional support of the child by agencies other than the mother decreases the age at which the mother should force the child to walk independently. In some cases, especially for the lightest mothers, it is never in the mother's best energetic interest to carry her child.
本文研究了母亲在抱孩子方面的投入，并提出了一种方法，用于确定母亲抱孩子而非迫使孩子独立行走在能量消耗上何时更具优势。我计算了行走时母亲和孩子的能量消耗，并制定了校正因子，以便于对幼儿进行这些能量计算。此外，我还研究了除孩子之外的母亲负担以及外部营养支持对能量消耗的影响。由于母亲的能量是一种有限资源，决定抱孩子还是迫使孩子独立行走尤为重要。这一决定可以根据母亲和孩子的体重以及孩子的年龄来预测。如果母亲提供孩子的所有营养，那么只有当母亲抱孩子时的能量消耗小于母亲和孩子独立行走时所消耗能量之和时，母亲才应选择抱孩子。然后可以确定两种消耗相等时的临界速度。还探讨了几个一般假设。一位体重60千克且孩子4岁的母亲的临界速度大约等于成年人的平均行走速度。对于体重较轻的母亲，孩子3岁时达到临界速度，而对于体重较重的母亲，直到孩子6岁时才达到这一点。除孩子体重之外的负担影响极小。母亲以外的机构对孩子的营养支持会降低母亲应迫使孩子独立行走的年龄。在某些情况下，特别是对于体重最轻的母亲，抱孩子从能量消耗角度来看对母亲永远不是最有利的。
