Biology Now, 2e

312 ■ CHAPTER 17 Animals and Human Evolution

BIODIVERSITY

four Neanderthal fossils in 2004) was compared

to modern human mitochondrial DNA, and the

tests showed that there was no genetic over-

lap between the species. Mitochondrial DNA

(mtDNA) is unique because it is passed down

virtually unchanged from mother to child, so

it can be tracked from one generation, or one

species, to another (Figure 17.11). But modern

Homo sapiens did not have Neanderthal mito-

chondrial DNA, so it appeared there was no

interbreeding, at least not involving female

Neanderthals.

That mitochondrial work was performed

by Svante Pääbo and researchers at the Max

Planck Institute for Evolutionary Anthropology

in Leipzig, Germany. Pääbo is one of the found-

ers of the effort to use genetics to study early

Hominins United

“For years, it was a very simple story: Neander-

thals either disappeared quickly when modern

humans came or they integrated with humans,”

says Condemi. But she suspected that the

dynamic was more complex. “In some regions,

Neanderthals disappeared very quickly. In other

regions, we have evidence the two [species]

could have overlapped.” Researchers, including

Condemi, had often suggested that during the

overlap, Neanderthals and humans interbred.

But there was little physical evidence.

Even DNA evidence initially suggested that

there was no interbreeding. DNA from the mito-

chondria of Neanderthals (isolated first from a

single Neanderthal fossil in 1997 and then from

Australopithecus africanus

(3 mya)

Homo habilis

(1.9–1.6 mya)

Homo erectus

(1.5 mya)

Homo sapiens

(anatomically modern humans

200,000 years ago to present)

Australopithecus

afarensis (3.5 mya)

The braincase is relatively small.

Skull and teeth resemble those

of other apes, not humans.

The braincase is larger. Skull and

teeth depart from those of other apes.

The Homo lineage split

from the Australopithecus

lineage.

All five hominins shown here

walked upright on two legs.

Figure 17.10

A gallery of hominin skulls

This tree shows the evolutionary relationships and the skulls of five hominin species. A complete

evolutionary tree of hominins would be “bushier,” with multiple side branches emerging at different times.

Q1: Where would the Neanderthal species branch be on this tree?

Q2: How would the Neanderthal skull differ from the Homo erectus skull?

Q3: How would the Neanderthal skull differ from the Homo sapiens skull?