Ecology and Primates

Primate Behavior • Primates are social

animals and most species live and travel in groups.

• A community is a unit of primate social organization composed of 50 or more individuals who inhabit a geographical area.

Primate Behavior • Males and females can be organized into

dominance hierarchies, an observed ranking system ordering individuals from high (alpha) to low standing corresponding to predictable behavioral interactions including domination.

Grooming• The ritual cleaning of

another animal to remove parasites and other matter from its skin or coat is a common pastime for both chimpanzees and bonobos.

• Grooming can be a gesture of friendliness, closeness, appeasement, reconciliation, or even submission.

Communication• Primates have elaborate systems of

communication based on vocalizations and gestures.

• Bonobos employ trail signs to communicate their whereabouts to others.

• Chimpanzees use facial expressions to convey emotional states.

• It is now clear that all of the great ape species can develop language skills to the level of a 2-to-3 year-old human child.

Tool Use• A tool may be defined as

an object used to facilitate some task or activity.

• From adults, juveniles learn to use a variety of tools and substances for various purposes.

• Innovations made by one individual may be adopted by other animals, standardized, and passed on to succeeding generations.

Chimpanzee Tool Use• A wild chimp is using

a long stick stripped of its side branches to fish for termites. Chimps will select a stick when still quite far from a termite mound and modify its shape on their way to the snacking mound.

Primate Tendencies• Brain Complexity (the brain

areas devoted to thought, memory and association are more elaborate and proportionally larger).

• Parental Investment (single offspring births combined with longer development periods).

• Sociality (strongly associated with parental investment, cooperative social groups are selected for in part because of the needs arising from primate parenting).

Human-Primate Similarities • Adaptive Flexibility

Through Learning• Neotony and life in cooperative social groups allows primates to learn behavior from their fellows, rather than relying only on genetically encoded behaviors.• Learned behavior has been observed in monkeys as well as apes.

Human-Primate Similarities • Predation and Hunting• Hunting is a regular and normal component of wild chimpanzee behavior.• Hunting by chimps is both opportunistic and planned.• Wild chimpanzees have been observed hunting consistently, using cooperative techniques, with some sex specialization (males hunt more than females).

Human-Primate Similarities• Tools• Tool use allows primates to adapt to a wider range of

niches more quickly than physiological adaptation alone (although primates are not the only animals that use tools).• Wild chimps have been observed constructing tools.

Human-Primate Similarities• Aggression and Resources• The capacity for hunting

exists among many different primates, but expression of this capacity can depend upon environmental pressure and opportunity.• Observations of chimps and

orangutans indicate that aggressive behavior (“warfare,” in some chimp cases) may increase when territorial encroachment occurs.

Ecology and Primates

Behavioral Ecology and Fitness• According to evolutionary

theory, when the environment changes, natural selection starts to modify the population’s pool of genetic material.

• Natural selection has another key feature: the differential reproductive success of individuals within the population.

Behavioral Ecology and Fitness• Behavioral ecology studies

the evolutionary basis of social behavior. • It assumes that the genetic

features of any species reflect a long history of different reproductive success (that is natural selection).• In other words, biological traits

of contemporary organisms have been transmitted across the generations because those traits enable their ancestors to survive and reproduce more effectively than their competition.

Behavioral Ecology and Fitness

• Natural selection is based on differential reproduction. Members of the same species may compete to maximize their reproductive fitness- their genetic contribution to future generations.

• Individual fitness is measured by the number of direct descendants an individual has.

Behavioral Ecology and Fitness

• Illustrating a primate strategy that may enhance individual fitness are cases in which male monkeys kill infants after entering a new troops.

• Destroying the offspring of other males, they clear a place for their own progeny.

Behavioral Ecology and Fitness• Besides competition,

one’s genetic contribution to future generations also can be enhanced by cooperation, sharing, and other apparently unselfish behavior.

• This is because of inclusive fitness – reproductive success measured by the genes one share with relatives.

Behavioral Ecology and Fitness• By sacrificing for their kin – even if this means

limiting their own direct reproduction – individuals actually may increase their genetic contribution (their shared genes) to the future.

• Inclusive fitness helps us understand why female might invest in her sister’s offspring, or why a male might risk his life to defend his brother.

Behavioral Ecology and Fitness• If self-sacrifice perpetuates more of their genes

then direct reproduction does, it makes sense in terms of behavioral ecology.

• Such a view can help us understand aspects of primate behavior and social organization.

Behavioral Ecology and Fitness• Maternal care always makes sense in terms of reproductive

fitness theory, because females know their offspring are their own. But it is harder for males to be sure about paternity.

• Inclusive fitness theory predicts that males will invest most in offspring when they are surest the offspring is theirs.

• Gibbons, for example, have strict male-female pair bonding, which makes it almost certain that the offspring are those of both members of the pair.

Behavioral Ecology and Fitness• Thus we expect male

gibbons to offer care and protection to their young, and they do.

• However, among species and in situations in which a male can’t be sure about his paternity, it may make more sense to invest in a sister’s offspring than a mate’s, because the niece or nephew definitely share some of that male’s genes.

Sociobiology and Fitness• “Sociobiology is the study of the evolutionary basis for behavior.”• Types of Fitness• Individual fitness is the number of direct descendents an

individual organism has.• Inherent in this notion, as seen in terms of natural selection, is

the implication that any individual’s fitness competes with that of its conspecifics.• A model attributing a drive to protect one’s individual fitness

to all organisms could not explain altruistic or self-sacrificing behavior.• Inclusive fitness is a theoretical concept developed to account

for unselfish behavior and is defined as “reproductive success measured by the representation [in succeeding generations] of genes one shares with other, related animals”.

Primate Evolution• The fossil record

offers evidence for no more than 5% of extinct types of primates.

• Such small numbers provide the merest glimpse of the diverse bioforms – living beings- that have existed on Earth.

Chronology• Based on fossils found in

Stratigraphy sequence, the history of vertebrate life has been divided into three main eras:

• The Paleozoic (544-245 m.y.a.): was the era of ancient life –fishes, amphibians, and primitive reptiles.

• The Mesozoic (245-65 m.y.a.): was the era of middle life – reptiles, including the dinosaurs.

• The Cenozoic (65 m.y.a. – present) is the era of recent life – birds and mammals. Each era is divided into periods; the periods, into epochs.

Chronology• Anthropologists are

concerned with the Cenozoic era, which include two periods:

• Tertiary and Quaternary.• Each of these periods is

subdivided into epochs.• The Tertiary had five

epochs: Paleocene, Eocene, Oligocene, Miocene, and Pliocene.

• The Quaternary includes just two epochs: Pleistocene and Holocene, or recent.

Chronology• Sediments from the Paleocene epoch (65-54

m.y.a.) have yielded fossil remains of diverse small mammals, including, by the late Paleocene, the earliest known primates.

• Hominoids became widespread during the Miocene (23-5 m.y.a.). Hominins first appeared in the late Miocene, (5-2 m.y.a.)

Early Primates• When the Mesozoic era

ended, and the Cenozoic era began ,around 65 million years ago, North America was connected to Europe but not to South America (The Americas joined around 20 million years ago.)

• Over millions of years, the continents have “drifted” to their present location.

Early Primates• During the Cenozoic, most

landmasses had tropical or subtropical climates.

• The Mesozoic era had ended with a massive worldwide extinction of plants and animals, including the dinosaurs.

• Mammals eventually replaced reptiles as the dominant large land animals.

• Trees and flowering plants soon prolifered.

Early Primates• According to the

arboreal theory, primates became primates by adapting to arboreal life.

• The primate traits and trends discussed previously developed as adaptations to life high up in the trees.

• A key feature was the importance of sight over smell.

Early Primates• Changes in the visual apparatus were adaptive in

the trees, where depth perception facilitated leaping.

• Grasping hands and feet were used to crawl along slender branches, Grasping feet anchored the body as the primates reached for foods at the ends of branches.

• Early primates probably had omnivorous died base on foods available in the trees.

Early Cenozoic Primates• A tiny, complete skeleton from China, first

described in 2013, represents the earliest known primate.

• The creature was smaller than today’s smaller primate- the pygmy mouse lemur of Madagascar. Named Archicebus archilles.

Early Cenozoic Primates• Archicebus

Archilles weighted no more than 1 ounce, and it had a 5-inch tail that was longer than its 4-inch body.

• It lived 55 million years ago, when Earth was a natural greenhouse.

Early Cenozoic Primates• This finding supports the view

that the first primates evolved in Asia – not too long after the extinction of dinosaurs 66 million years ago.

• Somehow primates crossed open water to reach Africa by 38 million years ago (Africa remained an island continent until 16 million years ago).

• Archicebus achilles had the feet of a small monkey; the arms, legs and teeth of a very primitive primate; and primitive skull with very small eyes.

Oligocene Anthropoids• During the Oligocene epoch (34-23 m.y.a.),

anthropoids became the most numerous primates.

• Most of our knowledge of early anthropoids is based on fossils from Egypt’s Fayum deposits.

• This area is a desert today, but 34-31 million years ago it was a tropical rain forest.

• The anthropoids of the Fayum lived in trees and ate fruits and seeds.

Oligocene Anthropoids• Compared with prosimians,

they had fewer teeth, reduced snouts, large brains, and increasingly forward-looking eyes.

• Of the Fayum anthropoid fossils, one group is the more primitive and perhaps is ancestral to the New World monkeys.

• These proto-monkeys were small (2-3 pounds), with similarities to living marmosets and tamarins, small South American monkeys.

Oligocene Anthropoids• Another Fayum group

seems ancestral to the catarrhines- Old World monkeys, apes, and humans.

• In 2013, researchers working in Tanzania’s Rukwa Rift Basin reported their discovery of two finds that may be the oldest known fossils from two major primate groups.

• hominoids (apes and humans) and Old World monkeys.

Oligocene Anthropoids• Geological dating shows the fossils to be 25.2

million years old, several million years older than any other confirmed example of an ancient ape or old monkey.

Miocene Hominoids• Hominoid fossils become abundant during the

Miocene epoch (23-5 m.y.a.), which is divided into three parts:

• Lower or earlier• Middle • Upper or later

Miocene Hominoids• The earlier (23-16 m.y.a.) was a warm and wet period,

when forests covered East Africa. The earliest hominoids are here called protoapes, or simply apes. Although some of these may be ancestral to living apes, none is identical, or often even very similar, to modern apes.

• Proconsul is the name for a group (three known species) of early Miocene protoapes.

• These ancient apes, which lived in Africa, had teeth with similarities to those of living apes.

• Below the neck, however, their skeleton was more monkeylike. • The Proconsul species ranged in size from that of a small monkey to that of a chimpanzee.

Later Miocene Apes• During the early Miocene (23-16 m.y.a.), Africa

had been cut off by water from Europe and Asia. • During the middle Miocene, Arabia drifted into

Euroasia, providing a land connection between Africa, Europe and Asia, were various animals, including hominoids migrated in and out of Africa.

Later Miocene Apes• The most remarkable Miocene

ape was Gigantopithecus- almost certainly the largest primate that ever lived.

• Confined to Asia, it persisted for millions of years, from the Miocene until 400,000 years ago, when it coexisted with members of our own genus, Homo erectus.

• Some people think Gigantopithecus is not extinct yet, that we know it today as the yeti or Bigfoot (sasquatch).

Later Miocene Apes• With a fossil record consisting of nothing more

than jawbones and teeth, it is difficult to say for sure just how big Gigantopithecus was.

• Based on ratios of jaw and tooth size to body size of other apes, various reconstruction have been made.

Later Miocene Apes• All reconstructions agree, however, that

Gigantopithecus was the largest ape that ever lived.

• There were at least two species of Gigantopithecus: one coexisted with H. erectus in China and Vietnam, and the other, much earlier (5 m.y.a.), lived in northern India.

Pierolapithecus Catalaunicus• In 2004, Spanish anthropologists announced their

discovery of what may be the last common ancestor of humans, chimpanzees, gorillas and orangutans.

• This ape species, named Pierolapithecus Catalaunicus, lived around 13 million years ago, during the middle Miocene.

Pierolapithecus Catalaunicus• The fond comes from a rich fossil site near the

village of Hostalets de Pierola in Catalonia, Spain.

• The find appears to represent a single adult male that weighted about 75 pounds. Like chimps and gorillas, Pierolapithecus was well adapted for tree climbing and knuckle-walking on the ground.

• Several features distinguished Pierolapithecus from the lesser apes (gibbons and siamangs) and monkeys.