ACT Reading Dec. 2015 72E - Passage II

Passage A by Stephen S. Hall

One of the longest and most heated controversies

in human evolution rages around the genetic relation-

­ship between Neanderthals and their European succes-

­sors. Did the modern humans sweeping out of Africa
₅ beginning some 60,000 years ago completely replace

the Neanderthals, or did they interbreed with them? In

1997 the latter hypothesis was dealt a powerful blow by

geneticist Svante Paabo-then at the University of

Munich-who used an arm bone from the original
₁₀ Neanderthal man to deliver it. Paabo and his colleagues

were able to extract a tiny 378-letter snippet of mito-

­chondrial DNA (a kind of short genetic appendix to the

main text in each cell) from the 40,000-year-old speci-

­men. When they read out the letters of the code they
₁₅ found that the specimen's DNA differed from living

humans to a degree suggesting that the Neanderthal and

modern human lineages had begun to diverge long

before the modern human migration out of Africa. Thus

the two represent separate geographic and evolutionary
₂₀ branches splitting from a common ancestor. If there

was any interbreeding when they encountered each

other later, it was too rare to leave a trace of Nean­-

derthal mitochondrial DNA in the cells of living

people.

₂₅ Paabo's genetic bombshell seemed to confirm that

Neanderthals were a separate species.

However, "During this time of the biological tran­-

sition," says Erik Trinkaus, a paleoanthropologist at

Washington University in St. Louis, "the baste behavior
₃₀ [of the two groups] is pretty much the same, and any

differences are likely to have been subtle." Trinkaus

believes they indeed may have mated occasionally. He

sees evidence of admixture between Neanderthals and

modern humans in certain fossils, such as a 24,500-
₃₅ year-old skeleton of a child discovered at the Por­-

tuguese site of Lagar Velho. and a 32,000-year-old skull

from a cave called Muierii in Romania.

Katerina Harvati, a researcher at the Max Planck

Institute in Leipzig, has used detailed 3-D measure-
₄₀ ments of Neanderthal and early modern human fossils

to predict exactly what hybrids between the two would

have looked like. None of the fossils examined so far

matches her predictions.

The disagreement between Trinkaus and Harvati is
₄₅ hardly the first time that two respected paleoanthropol­-

ogists have looked at the same set of bones and come

up with mutually contradictory interpretations. Ponder-

ing-and debating-the meaning of fossil anatomy will

always play a role in understanding Neanderthals.


Passage B by the editors of Scientific American

₅₀ In June of 2009 the famed Lucy fossil arrived in

New York City. The 3.2-million-year-old partial skele­-

ton of Australopithecus afarensis could attract hundreds

of thousands of visitors over the course of her four­-

month engagement-part of a six-year tour.

₅₅ Before this tour,Lucy had never been on public

display outside of Ethiopia. One might expect scholars

of human evolution to be delighted by the opportunity

to share the discipline's crown jewel with so many

members of the science-interested public. But news
₆₀ reports announcing her New York debut included the

same objections that aired when she first landed in the

U.S: namely, that the bones could sustain damage and

that the tour takes a key specimen out of scientific cir­-

culation for too long. Indeed, some major meseums
₆₅ turned the exhibit away in part for those reasons

The objections reflect a larger problem of posses­-

siveness in the field of human origins. Indeed. fossil

hunters often block other scientists from studying their

treasures, fearing assessments that could scoop or dis-
₇₀ agree with their own. In so doing. they are taking the

science out of paleoanthropology.

Critics of such secrecy commonly point to the case

of Ardipithecus ramidus, a 4.4-million-year-old human

ancestor discovered by Tim White of the University of
₇₅ California. Berkeley. Fifteen years after White

announced the first fossils of A. ramidus and touted the

importance of this species for understanding human ori­-

gins, access to the specimens remains highly restricted.

White, for his part, has said that be published only
₈₀ an initial report and that normal practice is to limit

access until publication of a full assessment And he

has noted that the condition of a key specimen-a badly

crushed skeleton-has slowed the release of the team's

detailed report.

₈₅ The scientists who unearth the remnants of human-

ity's past deserve first crack at describing and analyz­-

ing them. But there sh«?uld be clear limJts on this period

science is impeded: outside researchers can neither
₉₀ reproduce the discovery team's findings nor test new

hypotheses.