Most mammals reach sexual maturity when their growth rates are in decline, whereas humans experience a growth spurt during adolescence. Whether apes experience an adolescent growth spurt is still undecided. In the 1950s, data on captive chimpanzees collected by James Gavan appeared devoid of evidence of an adolescent growth spurt in these apes. In a recent reanalysis of Gavan's data, however, zoologist Elizabeth Watts has found that as chimpanzees reach sexual maturity, the growth rate of their limbs accelerates. Most biologists, however, are skeptical that this is a humanlike adolescent growth spurt. While the human adolescent growth spurt is physically obvious and affects virtually the entire body, the chimpanzee's increased growth rate is detectable only through sophisticated mathematical analysis. Moreover, according to scientist Holly Smith, the growth rate increase in chimpanzees begins when 86% of full skeletal growth has been attained, whereas human adolescence generally commences when 77 percent of full skeletal growth has occurred.