Chapter 22 – The Evolution of Primates
Paleoanthropology
the study of human evolution
Primate characteristics
1. 5 digits
2. opposable thumbs or toe
3. long freely moving limbs
4. eyes in front of the head
5. relatively large brain
6. flexible hands & feet
7. nails
3 sub orders or primates
1. suborder prosimii - lemurs
2. suborder tarsiiformers- tarsiers
3. suborder anthropoidea- monkeys, apes, humans
Suborder Anthropoidea
45 mya originated in asia & africa more developed cerebrum new world vs old world monkeys old world = africa and asia and europe short to no tails, nostrils downward, intensely social, ground dwellers new world = south and central america long tail, shorter thumbs or absent, aboreal, nostrils flat and open to side & social hominOIDS descended: old world monkeys 23-24 mya larger brain lack tail apes -gibbons, orangutans, gorillas, chimpanzees humans- a group composed of apes, and hominIDS (humans and their ancestors) hominids differences part 1 ape vs humans difference between apes and humans: humans: 1) complex curvature of the spine
2) shorter, broader pelvis
3) foramen magnum at base of skull
4) first toe aligned with other toe hominids differences part 2 ape vs humans human vs gorilla heads
1. human skull lacks the supraorbital ridge
2. has a pronounced chin
3. human brain is larger
4. teeth are arranged in a U shape
Sahelantropus tchadensis earliest known hominid, small brain, face and teeth had many char. of larger brained human ancestors. mix ape and huminid features
MORE human than ape
Orrorin
early hominid - about 6 mya probably walked upright and was bipedal based on fossil leg bones
Australopithecines
include: ardipithecus and australopithecus species australopithecus species- bipedal ( a hominid feature)
Genus Homo
Genus Australopithecus contains the immediate ancestors of genus Homo
Homo habilis
Earliest known hominid
- including slightly larger brain
H. Habilis fashioned crude tools from stone
Homo erectus part 1 larger brains than H. habilis
-made more sophisticated tools
-may have worn clothing, built fires lived in caves or shelter. fossils may actually be 2 species
Homo erectus part 2
Homo ergaster - earlier african species, gave rise to archaic Homo sapiens
Homo erectus - later Asian offshoot, maybe evolutionary dead end
Archaic Homo sapiens regionally diverse descendants of H. erectus or H. Ergaster
- in Africa, Asia, and Europe about 400k or 200k y/o
Brain about same size as our brains
- skulls retained some ancestral characteristics
-rich and varied cultures
Neandertals
230k to 30k y/o short sturdy builds
- receding chins and foreheads
- heavy supraorbital ridges and jawbones
- large front teeth
- nasal cavities with triangular bony projections
Chapter 32 – The Deuterostomes
Symmetry – general, structured body plan.
Coelom – fluid-filled body cavity surrounded by mesoderm-derived tissue.
Triploblastic – having three layers of cells during development: the endoderm, ectoderm, and mesoderm.
Deuterostomes – coelomate animals whose embryogenesis includes the blastopore developing into the anus of the animal.
Segmentation – division of the body into separate, sequential cavities.
Closed circulatory system – when blood is maintained in interconnected blood vessels and not mingled with other body fluids.
Cephalization – concentration of sensory and neural organs at the anterior end of an animal.
Metamorphosis – a restructuring of body shape and structure during development; typically from a juvenile to an adult form.
Filter-feeding – a method of heterotrophy, whereby a medium (typically water) passes by the animal and any suspended particulate items are “filtered” from the medium and ingested by the organism.
Classification
In the previous summaries on simple animals and protostomes, we explored much of Kingdom Animalia. In this summary we look at the remaining animals, those described as deuterostomes. Below is a review of the current classification of animals, based on morphology and development. You should familiarize yourself with the major anatomical and developmental differences that define animal phyla.
The traditional phylogeny is shown below. It is based on the following anatomical / developmental traits:
 Presence / absence of true tissues
 Type of body symmetry
 Presence / absence of body cavity (coelom)
 Pattern of coelom development (acoelom, pseudocoelom, true coelom)
The grades of animal evolution are as follows (italics – taxa described here):
1. No true tissues (only non-specialized cells) : Parazoa
2. True tissues (functionally-specialized cells) : Eumetazoa A. Radial symmetry, diploblastic (2 germ layers during development) : Radiata B. Bilateral symmetry, triploblastic (3 germ layers) : Bilateria
1) No body cavities or blood vascular system : Acoelomates
2) Body cavities and blood vascular system
a. Body cavity not enclosed in mesoderm : Pseudocoelomates
b. Body cavity enclosed in mesoderm : Coelomates
i) Early development includes spiral and determinate cleavage, mouth developing from blastopore, and schizocoely : Protostomes ii) Early development includes radial and indeterminate cleavage, anus developing from blastopore, and eterocoely : Deuterostomes