138 CHAPTER 6 | Macroevolution and the Early Primates
antibodies directed against it. Antibodies are proteins
produced by organisms as part of an immune response to
an infection. The technique relies on the notion that the
stronger the biochemical reaction between the protein
and the antibody (the more precipitate), the closer the
evolutionary relationship. The antibodies and proteins of
closely related species resemble one another more than
the antibodies and proteins of distant species.
Sarich made immunological comparisons between
a variety of species and suggested that he could establish
dates for evolutionary events by calculating a molecular
rate of change over time. By assuming a constant rate of
change in the protein structure of each species over time,
Sarich used these results to predict times of divergence
between related groups. Each molecular clock needs to
be set, or calibrated, by the dates associated with a known
event, such as the divergence between pro simian and an-
thropoid primates or Old World monkeys and apes, as es-
tablished by absolute dating methods.
Using this technique, Sarich proposed a sequence of
divergence for the living hominoids showing that human,
chimp, and gorilla lines split roughly 5 mya. He boldly statedcivilization. The Himalayas are some of the youngest moun-
tains of the world. They began forming during the Miocene
when the Indian subcontinent collided with the rest of
Eurasia, and they have been becoming taller ever since.
In honor of the Hindu religion practiced in the region
where the fossils were found, the contender was given
the name Ramapithecus, after the Indian deity Rama and
the Greek word for “ape,” pithekos. Rama is the physical
embodiment, or incarnation, of the major Hindu god
Vishnu, the preserver. He is meant to portray what a perfect
human can be. He is benevolent, protects the weak, and
exemplifies all noble human characteristics. Features like
the relative delicacy and curvature of the jaw and palate
as well as thick tooth enamel led paleoanthropologists
David Pilbeam and Elwyn Simons to suggest that this was
the first hominoid to become part of the direct human
line. They suggested that Ramapithecus was a bipedal tool
user—the earliest human ancestor. With these qualities,
Ramapithecus was perfectly named.
Other Miocene apes were also present in the foothills
of the Himalayas. Sivapithecus was named after the Hindu
deity Shiva, the god of destruction and regeneration. In the
Hindu religion Lord Shiva is depicted as an asocial hermit
who, when provoked, reduces his enemies to smoldering
ashes in fits of rage. Though never considered a human
ancestor, Sivapithecus also had the humanlike character-
istic of thick molar tooth enamel (unlike the African apes
but like the orangutans). Sivapithecus also had large pro-
jecting canine teeth more suitable to a destroyer than to a
human ancestor. The Sivapithecus and Ramapithecus fos-
sils were dated to between 7 and 12 mya.
The interpretation of these fossils changed with dis-
coveries in the laboratory. By the 1970s, scientists had be-
gun using biochemical and genetic evidence to establish
evolutionary relationships among species. Vince Sarich, a
biochemist at the University of California, Berkeley, was
working in the laboratory of Allan Wilson (see Anthro-
pologist of Note) and developed the revolutionary con-
cept of a molecular clock. Such clocks help detect when
the branching of related species from a common ancestor
took place in the distant past.
Sarich used a molecular technique that had been
around since the beginning of the 20th century: compari-
son of the blood proteins of living groups. He worked on
serum albumin, a protein from the fluid portion of the
blood (like the albumin that forms egg whites) that can
be precipitated out of solution. Precipitation refers to the
chemical transformation of a substance dissolved in a
liquid back into its solid form. One of the forces that will
cause such precipitation is contact of this protein with
© The Natural History Museum, LondonIn the 1960s scientists identified two distinct species of Miocene
ape from the foothills of the Himalayas: Sivapithecus and Ramapith-
ecus. The smaller one, Ramapithecus, was proposed as a tool-using
species ancestral to humans. Molecular investigations along with new
fossil finds demonstrate that these specimens were actually the male
and female of the same species and ancestral to orangutans. This
well-preserved specimen from the Potwar Plateau of Pakistan proved
that Sivapithecus was ancestral to the orangutan.molecular clock The hypothesis that dates of divergences
among related species can be calculated through an examination
of the genetic mutations that have accrued since the divergence.© The Natural History Museum, London