Lecture 3- Primate evolution and diversity I Flashcards
1
Q
What does primate mean?
A
- first rank
- primates viewed as the highest rank, the name taken from how we refer to heads of churches and archbishops
- controversial nomenclature as Linnaeus identified similarities between monkeys and humans and has hence classified them together
2
Q
What does classification mean?
A
- groups organisms together into phyla, class, order, genus etc based on shared characteristics.
- e.g.: all bats have wings, all mammals produce milk
- knowing that bats have wings and the ancestor didn’t gives us little information as to where the split occured
3
Q
What does phylogeny mean?
A
- represents the evolutionary relationships between organisms (it’s an evolutionary tree), based on shared derived characteristics (synapomorphies).
- Shared primitive characteristics (symplesiomorphies) are not considered useful
4
Q
What are symplesiomorphies?
A
-shared derived characteristics on which a phylogenic tree is based
5
Q
What are symplesiomorphies?
A
-shared primitive characteristics, not considered useful for establishing a phylogenic tree
6
Q
What is this?
A
- the mammalian evolutionary tree
- primates are a small portion of the tree (red rectangle)
7
Q
What are the nearest relatives of primates?
A
-flying Lemurs (Dermoptera)
8
Q
What are the Euarchonta?
A
- means true ancestors, these are three groups that share a common ancestor from which humans have also eveolved
- the groups are:
1. Dermoptera (Flying Lemurs)
2. Primates
3. Scandentia (Tree shrews)= proposed basal link to primates, separated approx. 80 MYA
9
Q
How old are the earliest primate fossils, where were they found and what were the characteristics of those animals?
A
- 65-55 MY
- most found in America but also found in Asia and Africa (spread quickly)
- belonged to a now extinct group known as Plesiadapiformes
- small 20-30g, arboreal, insectivorous
- similar in appearance and habits to modern tree shrews -found two species:
1. Purgatorius (c. 64 MYO) - maybe the basal link of primates?
2. Dryomomys (c. 55 MYO) - maybe the ancestor of tree shrews and the basal link?
10
Q
What are the characteristics of primates in general? (9)
A
- Grasping hands and feet
- Opposable digits
- Finger nails (instead of claws)
- Hind limb-dominated locomotion (arms less strong)
- Reduced sense of smell (small noses
- Binocular vision
- Extended maternal care
- Large brains
- Relatively small number of teeth
11
Q
What are the three primate characteristics that are related to arboreal living?
A
- Grasping hands and feet
- Opposable digits
- Binocular vision
12
Q
What is this?
A
- comprehensive primate phylogeny
- 1st split: Plesiadaformes splitting into Strepsirrhines and Haplorrhines
- 2nd split: Haplorrhines split into Anthropoidea and Tarsiiformes (tarsiers)
- 3rd split: Anthropoidea split into Platyrrhines (New World Monkeys) and Catarrhines (Old World Monkeys)
- 4th split: Catarrhines split into Hominoidea and Cercopithecoidea
13
Q
What was the first split in primate evolution?
A
- the Plesiadaformes split into Strepsirrhines and Haplorrhines
- this occured approx 78-63 MYA
14
Q
How many species of Strepsirrhines are there and where do they occur?
A
- 110 species (about a quater of primate species)
- mostly in Madagascar, few in S Africa, SE Asia
15
Q
How many species of Haplorrhines are there and where do they occur?
A
- 280 species
- spread throughout the world, in Africa, Asia, America
16
Q
In which areas are there differences between Strepsirrhines and Haplorrhines?
A
- Nose
- Eyes
- Snout
- Teeth
- Hand
17
Q
How is the nose different in Strepsirrhines and Haplorrhines?
A
- Strepsirrhines: wet nose, nose pad (rhinarium) and nose slits
- Haplorrhines: dry nose, no nose pad and have nostrils
- Strepsirrhines have better sense of smell & use scent- marking, possibly associated with nocturnal existence
18
Q
How are the eyes different in Strepsirrhines and Haplorrhines?
A
Strepsirrhines:
- the back of the retina has a layer (the tapetum) that reflects light which allows for more light to be collected at the retina
- this is believed to be a nocturnal adaptation (increases light gathering abilities of the rod cells)
- mostly dichromatic (not colour vision)
Haplorrhines:
-have colour vision and no tapetum, poorer visual acuity in the dark (as they are diurnal)
19
Q
How is the snout different in Strepsirrhines and Haplorrhines?
A
Strepsirrhines:
- have larger snout and a better sense of smell
Haplorrhines:
- have a flatter profile and less prominent snouts
20
Q
How are teeth different in Strepsirrhines and Haplorrhines?
A
Strepsirrhines:
- incisors and canines modified into thin prominent teeth = toothcomb which is used for grooming and chewing off bark
Haplorrhines:
-comparable mammalian dentition
21
Q
How are hands different in Strepsirrhines and Haplorrhines?
A
Strepsirrhines:
- second digit is modified into a longer claw, used for grooming.
eg. Aye-ayes (Daubentonia madagascariensis) have extra long claw for food extraction (eat insect grubs)
Haplorrhines:
-“normal” hands
22
Q
What were the key changes in the evolution of Haplorrhines? (4)
A
- Reduced sense of smell
- Development of trichromatic vision
- Tendency to greater frugivory
- Loss of ability to synthesise Vit C
- Single GLO gene mutation that only codes for Vitamin C (this means the mutation only affects vit C and is otherwise non-detrimental, our ancestors survived thanks to having a high fruit content in their diet)
23
Q
What are some of the species that have lost the ability to synthesise Vitamin C and how do they survive?
A
-selection on the gene is neutral
- Species that have lost Vit C = High dietary vitamin C content (fruit usually)
- Human RDA approx 1 mg/kg/day
- Gorillas (20-30 mg/kg/day)
- Howler monkeys (88 mg/kg/day)
- Spider monkeys (106 mg/kg/day)
24
Q
What is the controversial fossil of a possible early Haplorrhine?
A
-Darwinius masillae (aka “Ida”)
- Most complete fossil primate ever found
- 47 Mya old - found in Germany
- Lacks toothcomb and second-digit claw (hence Haplorrhine)
- 60cm long - probably 600-900g
- Diet - frugivorous/herbivorous (Fur and stomach contents preserved)
- controversial as the line is there and the time between the find and publishing (1983-2009)
- some say it is a lemur but doesn’t have the basic characteristics!
- probably spread from Siberia then to Europe and then east to the Americas
25
What was the second split in primate evolution?
- Haplorrhines split into the Anthropoidea and the Tarsiiformes (tarsiers)
- Tarsiiformes: 9 species, all in SE Asia
- Anthropoidea: 270 species, Africa, Asia, Americas
26
What are the characteristics of the Tarsiers?
* Arboreal primates
* Eat insects and small vertebrates
* Generally small (t have a tapetum
* Nocturnal (but no tapetum)
* Entirely carnivorous - insects
-probably arose in Asia
27
What is a synapomorphy?
-a synapomorphy or synapomorphic character state is a trait that is shared ("symmorphy") by two or more taxa and inferred to have been present in their most recent common ancestor, whose own ancestor in turn is inferred to not possess the trait.
28
Are there any easily identifiable synapomorphies in Anthropoids?
- genuine synapomorphies for Anthropoids are difficult to identify (many are shared with tarsiers)
- but anthropoids did evolve a single, "simple" uterus, which is typically associated with a decreased litter size, often means an increase in individual maternal investment
29
What were the earliest Anthropoids like?
* Earliest anthropoids - Tarsier-like (\<100g)
* Probably arose in Asia
* Insectivorous and arboreal
- had shearing plates in their dentition= characteristic of species that need to crush the hard exoskeleton of insects
30
What is the Eosimias and what is its significance?
* At least 3 species
* Found in China
* 40-45 Mya -link between Anthropoids and Tarsiers
- split where primates and monkeys diverge
- also a possible candidate for the split (like Darwinius masillae)
31
What were the main changes in Anthropoids?
* Switch to diurnal existence
* Relatively stronger upper-arms)
* Change in locomotion
- less leaping from trees
- more swinging (brachiation)
• More herbivorous diet
- occurred in several lineages
• Trend towards larger body size
- although they remained small
- and, associated with herbivory
32
What was the third split in primate evolution?
- the Anthropoids split into the Platyrrhines (New World Monkeys) and the Catarrhines (Old World Monkeys)
- split occurred approximately 43 MYA
- the Platyrrhines consist of about 135 species, all occur in the Americas
- the Catarrhines consist of about 145 species and occur in Asia, Europe and Africa
33
How did the Platyrrhines (the New World Monkeys) get to the Americas?
- Floated to South America on a raft (distance = 1500km)
- Genetic evidence suggests that this happened at least twice!
- pregnant female?
- female with young?
- multiple individuals?
- How did they survive without fresh water?
- Geological evidence = the rafts may have been “floating islands”
- most likely several individuals and probably on the floating island structures
34
How is the nose different in Platyrrhines and Catarrhines?
**Platyrrhines**
- wide flat noses
- nostrils well separated
**Catarrhines**
- narrow pointed noses
- nostrils close together
35
How is the tail different in Platyrrhines and Catarrhines?
**Platyrrhines**
- long,muscular,prehensile
- used to hold onto branches
**Catarrhines**
- less muscular, shorter
- sometimes absent
36
How are teeth different in Platyrrhines and Catarrhines?
Catarrhines
- lost a pre-molar (they have 2 incisors, 1 canine, 2 [not 3] pre-molars and 3 molars)
- Upper canine occludes against the first pre-molar
37
What are some of the other changes that occurred in the Catarrhines?
* General larger body size
* Greater sexual dimorphism
* Higher levels of sexual selection and competition between males
* Higher levels of polygyny
* Female sexual swellings
38
What were the earliest Catarrhines like?
-Aegyptopithecus zeuxis and Propliopithecus (2 species)
* 34 million years ago
* Found in Egypt (African origins)
* Body mass about 6kg
39
What is the fourth split in Primate evolution?
- the Catarrhines split into the Hominoidea (c. 20 species, Africa and Asia) and the Cercopithecoidea (Old World Monkeys, c. 125 species, Africa and Asia)
- occurred approx. 31 MYA
40
What are the differences between Cercopithecoids and Hominoids?
1. Tail:
- lost in Hominoids
2. Arms:
- Hominoid arms are long (as long or longer than legs)
- Numerous skeletal changes (arm movements more flexible)
41
What was the earliest Hominoid found?
-Proconsul
• Found in East Africa
- at least 3 species
* Earliest fossils ≈ 24 Mya
* Rainforest-dwelling, frugivorous, quadrapedal (not full flexibility of arms)
* Large monkey - about 30kg
42
What are the questions from this lecture?
1. What are the main groups of primates and how do they relate and differ from one another? 2. When did the major groups of primates originate? What does the fossil record tell us about the evolution of major primate groups? 3. What were the major evolutionary transitions that occurred in the evolution of primates in the lineage leading to man?
