Biology Now, 2e

316 ■ CHAPTER 17 Animals and Human Evolution

BIODIVERSITY

research and evidence will be necessary before

general agreement is reached regarding the

exact number of early Homo species and their

evolutionary relationships.

So, was the Neanderthal DNA found in

modern human genomes simply a remnant of

a common ancestor? In 2012, Pääbo’s team

and others were able to determine the age of

the pieces of Neanderthal DNA in the human

genome. They found that the DNA had been

introduced into our genome between 90,000

and 40,000 years ago, around the same time

that modern humans spread out of Africa and

met the Neanderthals. A remnant of DNA from

a common ancestor would have been 10 times

older.

All in the Family

The fossil record indicates that the first Homo

sapiens, called archaic H. sapiens, originated

between 400,000 and 300,000 years ago.

Taller and more robust than H. habilis,

H. erectus also had a larger brain and a skull

more like that of modern humans. It is likely that

by 500,000 years ago, H. erectus could use, but

not necessarily make, fire. In addition, H. erec-

tus probably hunted large animals, as suggested

by a remarkable 2010 discovery in Germany

of three 400,000-year-old spears, each about

2 meters long and designed for throwing with a

forward center of gravity (like a modern javelin).

H. erectus, or one of the other Homo ancestors,

migrated from Africa about 2 million years ago.

From there, this ancestor species spread around

the Middle East and into Asia. Homo fossils

dating from the period 1.9–1.7 mya have been

found in the central Asian republic of Georgia,

in China, and in Indonesia.

Overall, current research on H. habilis, H.

erectus, and other early Homo species indicates

that there were more species of Homo than was

once thought, and that several of these species

existed in the same places and times. More

Uniquely Human?

Y

es, the frontal lobe of the brain is unique to human

beings, and it enables us to reason like no other animal

on our planet. But what about the rest of the attributes

that we so commonly consider unique to us? Humans

pride themselves on their intelligence and deep

emotional connections to others, but are these really

only human traits?

● (^) Language. Researchers once believed language
was an exclusively human trait. We now know that
chimpanzees in the wild use sign language, with
approximately 70 different signs for distinct words.
Meanwhile, other primates, birds, whales, and
bats have distinct, learned vocalizations that they use
to communicate.
● (^) Memory. Some have suggested humans alone possess
the ability to store memories. But dogs easily learn
and remember many commands, while crows can learn
and remember shapes better than human adults can,
and they can use causal reasoning, not trial and error,
to unlock doors and find hidden objects.
● (^) Social culture. Once thought to be strictly human,
social culture is a learned trait that chimpanzees,
Japanese macaques, and killer whales pass on
throughout their populations. Tool use by dolphins,
elephants, and octopi varies in its specifics from
population to population—a sure sign of learned
behavior.
● (^) Emotions. Our emotions make us human, right? Others
in the animal kingdom have been documented express-
ing empathy (elephants), grief (dolphins, elephants),
jealousy (apes), curiosity (cats, lizards), altruism (apes),
and gratitude (whales). Apes have been seen laughing
at a clumsy fellow ape and using deception to outwit a
family member.
● (^) Self-Awareness. The ability to recognize oneself in
the mirror, or show self-awareness, was once thought
to be ours alone. As it turns out, all the apes, some
gibbons, elephants, magpies, and some whales pass
the mirror test of self-awareness.
● (^) Morality. Finally, what about a sense of morality or
an understanding of social norms? Monkeys and rats
will not accept offered food if, in doing so, a fellow
member of their species receives an electric shock.
To be sure, there is something unique about humans
that lies at the intersection of all these abilities. However,
our expanding knowledge of animal behavior can’t help but
make us feel more closely connected to the other species
with whom we share this planet.