The lifespan of Korean eunuchs
نویسندگان
چکیده
The chimpanzee fetuses used in our study showed a significant agerelated change in brain volume over the course of the study period (Figure 1B,C). The volume of the chimpanzee brain increased nonlinearly from 14 to 34 weeks of gestation (F = 634.28; cubic effect, p < 0.0001) (Figure 1C). The brain volume of the chimpanzee was only half that of the human fetus at 16 weeks of gestation (15.8 cm3; Figure 1C). The estimated volume of the human brain at the same gestational age is 33.6 cm3 [8]. At 32 weeks of gestation (just before birth), the volume of the chimpanzee brain reached approximately 40.3% of the adult volume. By contrast, the corresponding value for humans was 23.4%. However, the volume of the fetal human brain appears to continue to increase after this gestational age, as the volume of the human neonatal brain is ~30% of the adult volume (see Supplemental Experimental Procedures for details). Chimpanzee fetal brain growth velocity continued to increase from ~17 to 22 weeks of gestation (as also observed in human fetuses), although it was slower than that in human fetuses during this period. However, the velocity of brain growth in chimpanzee fetuses did not continue to increase after 22 weeks, whereas it did in human fetuses (Figure 1D). At 32 weeks of gestation, the velocity of chimpanzee brain growth slowed down to approximately 20% of that observed in humans (Figure 1D). The estimated rate of chimpanzee brain growth was 4.1 cm3/week at ~32 weeks of gestation (Figure 1D); in humans, the corresponding value was 26.1 cm3/week at the same gestational age (Figure 1D). These results demonstrate that the remarkable enlargement of the human brain already begins before ~16 weeks of gestation. Moreover, the growth velocity of brain volume increased until ~22 weeks of gestation in both chimpanzees and humans; however, after that time, brain growth in the chimpanzee fetus slowed down as birth approached. By contrast, brain growth in the human fetus continued to accelerate until around 32 weeks of gestation. Therefore, we infer that prenatal patterns of human neuronal enhancement changed from those of the chimpanzee during the rapid brain evolution of modern humans [9,10]. These ontogenetic patterns during intrauterine life appear to have emerged after the split of humans from chimpanzees and have contributed to the more marked brain size in our species.
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ورودعنوان ژورنال:
- Current Biology
دوره 22 شماره
صفحات -
تاریخ انتشار 2012