Lecture 6: Life in the Trees & Primates

Despite a few inaccuracies from a current perspective, this 1978 video reveals the basic primate patterns of morphology and behaviour. The trend over 60 million years is to binocular vision and increasingly better colour vision with lesser reliance on olfaction, more skilled grasping forelimbs, and cognition based on brain size. Primates also have increased in overall size, evolved greater social skills and continued a long period of maternal care of offspring.

According to the video’s narrator (David Attenborough), if one lives in the trees two of the most important physical features to have are forward facing eyes (3-D vision) to better evaluate distances and grasping hands. All primates have these, plus a number of other traits (such as pentadactyly, color vision, fingernails, opposable thumbs, tactile pads on the tips of the fingers, fingerprints, tendency toward trunk verticality, retention of the clavicle, large brain-to-body-size ratio) that constitute, when taken together, the hallmarks of the Primates.

[Species are in order presented in film – not necessarily in evolutionary groupings]


LEMURS

  • Most primitive (retaining ancestral traits) of all the primates
  • Ringtails, Sifaka, Indrii and others - Long snouts, wet noses, immobile faces / mobile ears, tactile vibrissa / toothcombs / Madagascar / Vertical clingers and leapers / Scent very important (stink fights / territoriality / urinating on hands and smearing on bark) / Also sound (indrii example) / Diurnal and Nocturnal


LORISES/Bushbabies

  • Much like lemurs, except live at night and in forests of Africa and southeast Asia / scent marking / Vert. clingers and leapers / nocturnal (to avoid competition)


TARSIERS

  • Insect eaters / no moist nose / Nocturnal


[ANTHROPOIDEA = all monkeys, all apes, humans – all have color vision]

MONKEYS - replaced lemurs / lorises in many niches; with one exception (owl monkey), monkeys are daytime creatures with excellent color vision.


American (or New World) Monkeys (50 plus species) [PLATYRRHINI]

Some species have developed prehensile (grasping) tails (derived trait)/ all species strictly arboreal (tree-dwelling) / species vary considerably in appearance and abilities but are generally thought to be more intelligent than lemurs and lorises / one species (the owl monkey) is strictly nocturnal

  • Marmosets - most primitive of So. America / genital displays instead of fights/ rely on scent marking / gum eaters.
  • Howlers - loudest mammalian noise / grasping tail / vegetarians / relatively weak sense of smell (note shape of skull and brain associated with these senses) / excellent color vision (food / mates / etc.) / leaf-eaters


Old World (Eurasian & African) Monkeys [CATARRHINI]

No prehensile tail / not as exclusively adapted to trees / many different dietary patterns (some species strictly vegetarian, some mostly fruit, some omnivorous) / some species larger than American monkey species / many different forms of social grouping & organization.

  • Vervets - African ground dwelling, elaborate calls denoting specific threats
  • Baboons: ground dwellers (except sleep in trees or on cliffs at night), large males, omnivores, visual signals (eyebrow flash). Have strict dominance hierarchies (or “pecking orders”) and complex "politics."
  • Macaques - Many, many different species. One of most adaptable of ALL primates: very adaptive to wide variety of environments. Live all over (from western and central Asia to Japan and southeast Asia and India, Africa). Film examined the Japanese snow monkeys: excellent examples of cultural behavior (hot tubbing, washing sweet potatoes in both fresh and salt water, separating rice grains from sand - Imo). Also saw good examples of opportunistic bipedalism.
  • Asian tree monkeys (silver leaf monkey) - leaf eaters / have developed highly specialized teeth and digestive system to make use of low-quality food.


HOMINOIDEA = apes + humans]: humans and their closest relatives. All are intelligent and have varied social structures and diets. No tails! (derived trait)

APES - humans’ closest relatives

Asian apes

  • Orangutans - very, very LARGE – show distinct size differences between males and females = sexual dimorphism) / mainly fruit eaters / tool makers and users (not shown)
  • Gibbons - smaller, more agile tree-dwelling apes, jumping and swinging through trees, many fractures (1/3 of all have broken bones) / very, very long arms and permanently curved finger and hand bones with very short thumbs related to the way they move through the trees = brachiation

African apes

  • Gorilla - Largest of all living primates, largely ground dwelling--eating, grooming, resting. Behavior is to a large extent governed by their diet -- widely available low calorie leaves, bark, even wood. Need to eat a lot – have specially adapted digestion to extract nutrients from these foods / live in “family” units: one silverback (male), perhaps 1-2 blackback males (blood relative of silverback), several adult females, children of silverback and females / foot no longer grasping / generally peaceful
  • Chimpanzees - omnivores (largely vegetarian though they eat whatever meat – termites, monkeys – they can get), still an agile tree dweller (size, foot remains dextrous, spends evening in tree nest), highly individualized faces, large, highly structured social groups (20-50), social function of grooming, make and use simple "tools" (e.g. termite stick)/ actively hunt (usually monkeys) / skills are learned (e.g., being a good mother) / our closest primate "cousin" (along with the bonobos, not mentioned in film).

At the end of the video, David Attenborough says that 15 mya our ancestors made the move out of the trees and onto the savanna. When this video was made in the late 1970s, this was our best guess. However, THIS IS WRONG. Anthropologists now believe that the first hominids (and the first chimpanzees) emerged from the generalized ancestral ape population much later in time. Chimps and humans separated by 5-7, not 15 million years!


II. OUTLINE OF PRIMATE GROUPS

Classification p.126 of text, images on lecture ppt Yes, you must know these groups for the test!

Strepsirhini - Open eye orbitals; mandible not fused; dental comb; no colour vision

  • Lemurs (Madagascar)
  • Lorises / Galagos (Asia & Africa)

Haplorhini: Tarsiers (Asia) + Anthropoidea

  • Anthropoidea (monkeys, apes, humans) – list of common features p. 130, including even more emphasis on categories above (lg brain, focus on vision), plus bony orbitals of eye sockets, mandible fused, generalized dentition; colour vision (film)
  • Platyrrhini (New World monkeys) – broader nostrils; 2.1.3.3 dentition (most); only monkeys w/ prehensile tails (and only some have this includes: marmosets, squirrel monkeys, howler monkeys, etc.
  • Catarrhini - (Old World monkeys, apes, human) – narrower nostrils, downward facing nose; 2.1.2.3 dentition
  • Cercopithecoidea - (Old World monkeys) includes: baboons (Africa, terrestrial) Japanese macaques (snow)
  • Hominoidea (apes & humans) – list of common characters p. 135, including more complex behaviour, no tails includes: orangutan (Asia, brachiator) gorilla (Africa, plants, knucklewalker) chimpanzee (Africa, omnivorous, inquisitive, much in trees, long childhood, lg groups, grooming, sight-oriented, recognize faces bonobo (not in film, very important) humans!


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