Chapter 8 Flashcards
Radiations
this population might evolve independently into a new species, changing to fit particular ecological niches in the new environment and never requiring natural selection to complete its reproductive isolation from the parent species.
Plesiadapiforms
archaic primates
Euprimates
true primates
Anthropoids
monkeys and apes
Old World
Africa
What are some of the factors that lead to primate diversity and evolution?
Climate change forced major extinctions as the northern continents became increasingly dry, cold, and seasonal and as tropical rainforests gave way to deciduous forests, woodlands, and eventually grasslands.
Diagnosis
The features that allow you to recognize a group
St. George Jackson Mivart
British naturalist who figured out what pattern every primate has that makes it a primate: nails, clavicles, placentation, orbits encircled by bone, three tooth types i.e., incisors, canines, premolars/molars), posterior lobe of the brain, calcarine fissure of the brain, opposable thumb and/or big toe, nail on the big toe, well-developed cecum, pendulous penis, testes within a scrotum, and two nipples in the pectoral region
Le Gros Clark
Expanded on St. George’s theory. Clark’s trends emphasize the flexibility and generalized nature of the limbs, mobility and dexterity of the digits, reduction of the snout with elaboration of the visual system, retention of simple teeth, and elaboration of the brain with prolonged period of juvenile dependence
Robert Martin
Expanded on both of their theories and emphasized distinctive reproductive characteristics of primates, along with details of cranial anatomy and grasping extremities
What are challenges in determining if a particular animal is a primate?
From the first modern attempts to classify primates, scientists have struggled to come up with traits that are possessed exclusively and universally by primates. In the end, most have generated lists of traits that are of variable utility in making a correct diagnosis.
Why are some of the traits Mivart decided on problematic?
Many primatologists have pointed out that no single feature on this list is unique to primates. Also, nails appear twice. Taken together, perhaps it is a useful list. Unfortunately, some of these traits e.g., three types of teeth) are neither clear nor true of all primates. Other traits, like nipple number and location, are quite variable among primates. Still others, for example the pendulousness of the penis, can be assessed in only males
What makes primates unique?
Instead, if there is something unique about primates, it is probably a group of features rather than one single thing
Frederic Wood Jones
credited with the Arboreal Hypothesis of primate origins which holds that many of the features of primates evolved to improve locomotion in the trees
What features do primate have that make moving through trees possible?
the grasping hands and feet of primates are well suited to gripping tree branches of various sizes and our flexible joints are good for reorienting the extremities in many different ways.
Matt Cartmill
studied and tested the idea that the characteristic features of primates evolved in the context of arboreal locomotion.
How does Cartmill’s theory differ from Jones’?
jones-> improve locomotion
Carmill->studied the evolution of primates in the context of arboreal evolution
Why did Cartmill begin to question Jones’ theory and what does he believe drove primate evolution?
Cartmill reasoned that there must be some other explanation for the unique traits of primates because other animals can climb trees without primate traits. His hypothesis emphasizes the primary role of vision in prey detection and capture; it is explicitly comparative, relying on form function relationships in other mammals and nonmammalian vertebrates. According to Cartmill, many of the key features of primates evolved for preying on insects in this special manner.
Robert Sussman
argued that the few primates that eat mostly insects often catch their prey on the ground rather than in the fine branches of trees. Furthermore, predatory primates often use their ears more than their eyes to detect prey. Finally, most early primate fossils show signs of having been omnivorous rather than insectivorous. Instead, he argued, the earliest primates were probably seeking frui
Paleocene
distinctive visual traits and extremities in the Paleocene approximately 65 million to 54 million years ago
Why some anthropologists unhappy with Cartmill’s visual predation hypothesis?
One reason for this is that many primates today are not especially predatory. Another is that, whereas primates do seem well adapted to moving around in the smallest, terminal branches of trees, insects are not necessarily easier to find there.
Eocene
Subsequent to the paleocene. Eocene approximately 54 million to 34 million years ago) just when angiosperms (flowering plants) were going through a revolution of their own
Diffuse coevolution
coevolution
D. Tab Rasmussen
noted several parallel traits in primates and the South American woolly opossum, Caluromy. He argued that early primates were probably foraging on both fruits and insects.
