- Three unfortunate youths who died about
800,000 years ago have provided a hint that the prolonged period of childhood
growth and development in humans has surprisingly old origins.
-
- This form of delayed maturation, accompanied
by protracted child care and a complex social life, is often regarded as
a hallmark of modern humans. However, the ancient youngsters, who may belong
to a species that preceded Homo sapiens, exhibit a tooth-development pattern
similar to that of people today, contends a research team led by paleobiologist
José M. Bermúdez de Castro of the National Museum of Natural
Sciences in Madrid.
-
- "This evidence supports the view
that as early as [800,000 years ago], at least one Homo species shared
with modern humans a prolonged pattern of maturation," the researchers
report in the March 30 Proceedings of the National Academy of Sciences.
-
- Bermúdez de Castro and his team
found the fossils in a cave in northern Spain's Atapuerca Mountains. They
assign the specimens to a new species, Homo antecessor, although other
investigators go no further than placing them in the Homo line (SN: 5/31/97,
p. 333).
-
- For each fossil individual, the scientists
noted the relative maturity of pairs of teeth from the front and back of
the mouth. The team then compared these data with dental measures obtained
by other researchers for living apes and humans, as well as for older fossils
in the human evolutionary family.
-
- Only the Spanish fossils exhibited a
pattern of dental development much like that of modern humans, with relatively
late eruption of many teeth, the investigators say. The third molar in
the Atapuerca specimens reached maturity sooner than in current European
populations, although the timing of its appearance lies within the worldwide
human range, they note.
-
- Analyses did not allow for precise chronological
age estimates for the three fossil individuals. Two died in early adolescence
and one as a young child, according to the researchers. One of the adolescents
exhibited a tooth deformation caused by a severe childhood growth disturbance.
-
- Humanlike dental development in the Atapuerca
fossils renders more plausible an earlier report that they had brain-case
volumes nearly as large as those of modern H. sapiens, Bermúdez
de Castro and his coworkers hold. The Spanish scientists had estimated
this volume from a cranial fragment believed to have come from one of the
fossil teenagers.
-
- "There's still some primitiveness
in these teeth, but they also show the delayed system of maturation seen
in modern humans," comments anthropologist F. Clark Howell of the
University of California, Berkeley. "The Atapuerca individuals seem
to have crossed some kind of growth-related Rubicon."
-
- The new study provides "the first
substantive evidence" for extended individual development before the
emergence of H. sapiens, adds anthropologist Tim Bromage of Hunter College
in New York City. Intriguingly, major abnormalities from the growth disturbance
that afflicted one of the Atapuerca youngsters likely required the child
to receive extensive care from adults, in Bromage's view. "I find
something human in that," he remarks.
-
- Neandertals, which lived from about 135,000
to 30,000 years ago, also exhibited a modern human life-history pattern,
presumably retained from ancestors such as those at Atapuerca, Bromage
says.
-
- If the new findings indeed come from
an earlier Homo species, they challenge the assumption that prolonged individual
development can serve as a distinguishing trait of modern humanity, the
New York researcher asserts.
-
- Much remains unknown about the pattern
and rate of growth in ancient human ancestors, according to Howell. Other
Atapuerca remains, which date to 300,000 years ago and belong to a Neandertal-like
species (SN: 4/10/93, p. 228), include juvenile specimens that the researchers
now can subject to dental analyses, he says.
-
- References:
-
- Bermúdez de Castro, J.M., et al.
1999. A modern human pattern of dental development in Lower Pleistocene
hominids from Atapuerca-TD6 (Spain). Proceedings of the National Academy
of Sciences 96(March 30):4210.
-
- Further Readings:
-
- Bower, B. 1997. Spanish fossils enter
human ancestry fray. Science News
- 151(May 31):333.
-
- ______. 1993. Neandertals take big step
back in time. Science News
- 143(April 10):228.
-
- Sources:
-
- José M. Bermúdez de Castro
- Musco Nacional de Ciencias Naturales
- Departamento de Paleobiología
- Consejo Superior de Investigaciones
Científicas
- J. Guitiérrez Abascal 2
- 28006 Madrid
- Spain
-
-
- From Science News, Vol. 155, No. 14,
April 3, 1999, p. 212. Copyright ©
- 1999, Science Service.
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