Could the fossils
found at Laetoli and Hadar, roughly a thousand miles apart and spanning more than
half-a-million years, have belonged to the same species? Each of the four dig sites
reveals only a partial picture: Lucy, while a 40 percent complete skeleton, has
only fragments of a skull. The skull found at Hadar in 1992 has no body. The Laetoli
prints are like the shadows of invisible creatures.
The difference in size between Lucy's petite bones and more massive
ones found at Hadar also puzzled paleoanthropologists. But careful analysis of
thousands of fossils, and a remarkable discovery, helped resolve the debate.
In the summer of 1977, collaborators Donald Johanson and Tim White
got together with a roomful of ancient hominids from Hadar and Laetoli. In addition
to the famous footprints, they had two well-preserved jaws and isolated teeth from
Laetoli. From Hadar, they had not just Lucy but a host of hundreds of fossils,
including a knee joint that strongly suggested its owner walked upright.
But the find that may have been most critical for relating the
various fossils to one another was the First Family. Here were the remains of 13
individuals -- likely 9 adults and 4 children, judging from their teeth and jaws.
If they all were entombed together, perhaps by a flash flood, they likely all
belonged to the same social group. And if they were an "extended family," they
were certainly all the same species. The adults of this group varied tremendously
in height and heft, leading White and Johanson to conclude that the males of this
species were tall and bulky compared to the females, like gorillas are today.
Johanson and White announced at a 1978 symposium in Stockholm
that Lucy, the people of Laetoli, the First Family, and other finds all belonged
to a single species: Australopithecus afarensis, the Southern Ape from Afar.
Anthropologists today continue to debate whether all of the individuals of the
First Family were truly buried together, and whether all of the Hadar and Laetoli
finds are truly members of the same species. Yet many agree that A. afarensis
was a critical species in the story of human evolution, and likely the common
ancestor to all later branches of humanity, including our own.
First Family: various teeth and bones
The wide range in body size among this one group of individuals lead many
anthropologists to think that Lucy, the Hadar skull, and other finds could be
from the same species. Some scientists suspect that one "extended family" of
13 individuals was entombed together in a flash flood; the fossils of the First
Family show few signs of weathering or attack by predators.