Biogeography and Humans

March 24, 2014

Humans

• Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

• Order: Primates

• Family: Homonidea

• Genus: Homo

• Species: Sapiens

• Subspecies: Homo sapiens sapiens

Other Primates

• Suborder: Haplorhini

– Humans, tarsiers (left), monkeys, apes

– Infraorder: Catarrhinni

• Humans, old world monkeys, apes

– Infraorder: Platyrrhinii

• New world monkeys

• Suborder: Strepsirhini

– Lemurs (above right), lorises (above left)

Primates

• Hominoidea – superfamily including humans, the small apes (gibbons - above), and the great apes (chimps, orangutans, gorillas)

• Similarities in blood and protein chemistry• Humans share 98% of DNA with chimps• Pentadactyl – having 5 fingers and toes• Prehensile – ability of hands and feet to grasp objects

Adaptations to Arboreal Existence?

• Prehensile hands and feet, shoulder and arm design

• color stereoscopic vision – for judging distance, identifying food and predators

• Low numbers of offspring• Molecular clock – when did humans diverge

from chimp ancestors?– mtDNA from mother– 5 to 10 mya

Early Primates• Arose 70 mya during late Cretaceous• Related by common ancestor to insectivores and bats• Extinct suborder Plesiadapiformes – appeared in North America 65

mya

• Humans have smaller digestive tracts, which means cooked food is processed faster

• Cooked food is easier to digest

• Humans have small mouths, weak jaws, small teeth, small stomachs, small colons, and small guts overall, smaller jaw muscles than great apes

• Humans have the smallest molars in relation to body size of any primate

• Great apes eat 2ce as much by weight per say as we do because their food is packed with indigestible fiber (30% by weight, compared to 5-10% in human diets)

• Our colons is less than 60% of the mass that would be expected for a primate of our size

• The colon is where the intestinal flora ferment plant fiber – because ours is so small we cannot utilize plant fiber as effectively for food

• The more gut tissue, to more energy expended on metabolism – small human gut saves us at least 10% daily energy expenditure

• In other carnivores, food stays in the stomach longer – dogs 2-4 hrs, cats 5-6 hrs, humans 1-2 hrs

• In carnivores, meat spends a long time in the stomach so the raw meat can be reduced and digested

• Figure 17.9

• Figure 17.12

• Figure 17.14

• Figure 17.16

• Figure 17.18

• Figure 17.19

Lessons from the Biogeography of Humanity

• On a global scale, human expansions were not gradual and continual, but episodic

• Early expansions of hominids were strongly influenced by the same types of geographic barriers, filters, and corridors that influenced our mammalian relatives

• Our range expansions on continents and across archipelagoes were the result of recurrent bouts of colonization and expansion

• Throughout our evolutionary history, the ability of humans to colonize distant sites and to modify, and eventually dominate, a greater variety of ecosystems has continually increased

Early Primates

• Early primate-like mammals were not immediately important following dinosaur extinction 65 mya

• The most dramatic changes were brought about by the emergence of large grazing and browsing mammals with tough hoofs, grinding teeth, and digestive tracts specialized for the processing of grass, leaves, and other fibrous plant materials.

Early Primates

• The beginning of the Eocene Epoch - appearance of early forms of most of the placental mammal orders that are present today

• Among them were primate species that somewhat resemble modern prosimians such as lemurs, lorises, and possibly tarsiers.

• This was the epoch of maximum prosimian adaptive radiation.

• Eocene prosimians lived in North America, Europe, Africa, and Asia. It was during this epoch that they reached the island of Madagascar.

Early Primates

• Monkeys evolved from prosimians during the Oligocene or slightly earlier.

– They were the first species of our suborder

• Several genera of these early monkeys have been identified—

– Apidium - fat squirrel (2-3 pounds),

– Aegyptopithecus - size of a large domestic cat (13-20 pounds)

• Both were probably fruit and seed eating forest tree-dwellers.

• Compared to the prosimians, these early monkeys had fewer teeth, less fox-like snouts, larger brains, and increasingly more forward-looking eyes.

Early Primates

Early Primates• 23 to 14 mya – great increase in ape

diversity and range• Beginning of Miocene, extensive

forests covered Africa and Eurasia• 20 different genera of Caterrhinii apes

from Africa, to western Europe, to southeast Asia– Pliopithecus – western Europe –

similar to modern gibbons– Gigantopithecus – China and India

– larger than modern gorillas• Ramapithecines – jaws and teeth like

humans and apes; skull like orangutans– 14 mya – climate changes

requiring adaptation to savanna climate

– Lived at forest edge– Bipedal – uses less energy– Reduced canines