UpDate - Vol. 12, No. 37, Page 6
July 22, 1993
In the News
Recent comments about the University and its community in the media
are featured in this regular column.
Demonic little pigs
Only a dozen or so schools around the country have a course on the
history of the environment. This spring, David Grettler is teaching one at
the University of Delaware. Grettler's idea was to offer a course that
focuses on how people have interacted with the environment over time.
Grettler, a research associate in anthropology whose work has focused on
the environment, says the course examines environmental concerns in early
Greek and Roman times, European culture and modern American culture as well
as several issues specific to Delaware.
One of those is the environmental archaeology of the construction of
state Route 1. Another issue important to the state's ecological history is
the story of the Leipsic swine petitions. From l780 to 1830, Grettler says,
only 40 percent of the state's residents owned land, while many others
owned pigs that ran loose over other people's property while breaking
through kitchens and causing a debacle, in at least one area, called the
Milford Pig War.
"There are some really funny accounts of demonic pigs breaking through
fences," Grettler says. "That old story that the pig ate my brother
probably wasn't so funny in Delaware."
"Pig Tales"
Delaware Today
May, 1993
Birth of the midwife
Childbirth is more hazardous in humans than in any other primates. And
using the length of labor as a measure, it is more difficult for a human
mother to give birth than it is for a non-human primate. Karen Rosenberg,
an anthropologist at the University of Delaware, thinks this means that at
no time in the history of Homo sapiens could mothers have given birth
without help.
Rosenberg reached her conclusions by taking a fresh look at how humans
acquired their mechanism for giving birth (Yearbook of Physical
Anthropology, vol. 35, p. 89). The human birth mechanism is unique: a baby
has to take a tortuous path through the birth canal, rotating its head
halfway through. This is because the sacrum and other pelvic bones are
arranged for upright posture, and because a fetus' head is large compared
with the rest of the body.
In all non-human primates, the birth canal is basically a straight
tube that throughout its length is wider from front to back...than it is
from side to side. In chimpanzees and gorillas, particularly, the baby's
head fits in the birth canal with room to spare.... So an ape birth is
comparatively simple.
By contrast, the human birth canal is a tunnel of varying cross
section.... This means that a human baby has to start its journey facing
the mother's side. Then in mid plane, where the transverse diameter of the
canal decreases, the head flexes to bring the chin down onto the chest and
it rotates through 90 degrees.... Finally, the head passes through the
rounded outlet-in a different orientation from the one in which it entered
the birth canal....
There is obviously a limit to how big the head of a human fetus can be
and still pass through the birth canal. This explains why, in modern
humans, the rapid brain growth that in most primates occurs only before
birth has to continue in infancy. Only when a baby is a year old does brain
growth slow down. So in terms of brain development, human gestation lasts
21 months.
No other primate has this pattern of brain growth and such a long
period of total infant dependence. In all other primates, including apes,
the pace of brain growth changes from the rapid fetal rate to the slower
post-fetal rate as soon as the baby is born.
But how did humans' unusual patterns of birth and development evolve?
Because the size and shape of the pelvic aperture determine the way an
infant is born, Rosenberg was able to make some deductions about the
evolution of the birth process from the pelvic bones of fossil humans....
Palaeoanthropologists have reconstructed pelvic girdles belonging to
"Lucy," the famous 3-million-year-old female Australopithecus afarensis
from Hadar in Ethiopia.... Present evidence suggests that Lucy's pelvis was
consistently widest from side to side and therefore more oval throughout
its whole cross section than a modern human pelvis.... There was ample room
for the fetal head....
A later stage in human evolution, early Homo erectus, is known from a
nearly complete skeleton from about 1.6 million years ago found at
Nariokotome on the west side of Lake Turkana, Kenya. Information from this
skeleton about the birth canal is, however, limited because it belonged to
a 12-year-old boy...
However, this hominid had long legs and narrow hips, and
palaeoanthropologists believe that the birth canal of its female
counterpart was too small to take a large-brained baby. (Studies) suggest
that for the Nariokotome boy's brain to reach the adult size, it would have
needed to continue to grow at a fast pace after birth as it does in modern
humans....
Neathanderthals (usually called Homo sapiens neanderthalensis)-a much
later stage in human evolution dating from around 130,000 to 30,000 years
ago-had brains the same size or slightly bigger even than ours. Rosenberg
suggests that their birth mechanism did involve rotations of the baby's
head, as in modern humans, and that the baby appeared facing the mother's
back. Along with brain expansion and this type of head presentation came
difficult deliveries and the need for midwives.
"On the origins of the midwife"
New Scientist
May, 1993
News from Tierra
The tropical rain forest is perhaps the most complex living system on
Earth. Scientists have long wondered how such elaborate biological order
could have risen from the chemical chaos that 4 billion years ago blanketed
this barren planet: So unlikely did the scenario seem that it has often
been likened to the spontaneous emergence of a jet airplane from a junk
heap.
But students of chemical evolution are now coming to believe that the
dawn of life on Earth wasn't so improbable after all. Scientists working
with both laboratory flasks and computer simulations of primitive life are
producing a clearer picture of how chemicals first stirred with vitality on
ancient Earth and ultimately evolved into the biological complexity that
includes every organism from microscopic parasites to humans....
With the help of computer models, scientists are gaining insight into
what happened just after the primordial ooze began metabolizing and
replicating, when early life started to branch out into new forms.
Among the most enlightening models is Tierra, designed by Thomas Ray
of the University of Delaware, as a test of Darwinian theory. Tierra is a
world "inhabitated" by computer programs-lists of simple instructions
analogous to genetic codes-that tell each digital organism how to live and
replicate.
Tierrans that compete most successfully for computer time and memory
space make the most copies of themselves.
Tierra reveals how random chance can produce systems of great
complexity and diversity. Tierrans copy themselves with errors-the
equivalent of mutations in genes-and this glitch in the system allows the
computer creatures to evolve. Ray started with a single ancestor program 80
instructions long-the equivalent of an RNA-based life form-and set the
world in motion in January 1990.
Evolution proceeded at a rate equivalent to millenniums per hours, and
overnight, dozens of mutated computer programs emerged. One, for example,
was only 22 instructions long, yet it could replicate six times faster than
the original ancestor.
Tierrans also diversify in much the same way that early life forms
must have. For instance, those with severely truncated lists of
instructions lost the ability to replicate, yet they found a way to
survive. These computer parasites borrowed instructions from their more
complete cousins, much as viruses use their hosts to enable them to
multiply. In fact, parasites may have played an indispensable role in
spurring evolution and diversity in all living systems.
As on Earth, the parasitic Tierrans usually provoke an arms race. The
hosts devise ever more clever ways to hide their codes, while the parasites
find wilier ways to get at them.
Tierra's results also suggest that living systems may be far more
resilient than previously thought. When Ray tinkered with Tierra's software
to generate extremely radical mutations, an even richer variety of faster,
fitter computer creatures evolved. "The life force is so powerful," says
Ray. "Life's clearly not the result of just a lucky shot."
Are Tierrans alive? A cadre of scientists contends that computer
programs capable of "metabolizing" computer energy to replicate, evolve and
even develop social interactions are as alive as the plants and animals in
a rain forest.
Living things don't have to be wet and squishy, they argue; they must
simply act like other living things. With the advent of artificial life
looming on the horizon, debate about life's ancient origins may soon shift
to how life will evolve in the future.
"Computing the primordial ooze
Scientists are modeling
the origins of life"
U.S. News & World Report
May 3, 1993