Albia Dugger Miami Dade College Cecie Starr Christine Evers Lisa Starr Chapter 24 Animals II: The Chordates (Sections )

24.9 Primate Traits and Evolutionary Trends Primates include humans and their closest mammalian relatives They have hands and feet capable of grasping objects primate Mammal having grasping hands with nails Includes prosimians, monkeys, apes, and hominids such as humans

A Primate A chimpanzee shows off its grasping five-digit hands and feet Primates have nails rather than claws

Primate Lineages An early branching separated anthropoids (monkeys, apes, and humans) from prosimians (lemurs and tarsiers) Hominoids include apes and humans Hominids are the most recent hominid Human or extinct humanlike species

Primate Classification

Primate Evolutionary Tree

Fig 24.23, p. 388 Tree shrewlike ancestor Hominids Old World monkeys LemursTarsiers New World monkeys GibbonsOrangutansGorillasChimpanzees Primate Evolutionary Tree

5 Key Trends in Primate Evolution 1. Structure of the face changed Early primates were shrewlike A flattened face, with eyes at the front of the skull, improved depth perception 2. Teeth and jaw were modified for a mixed diet

Evolution of the Primate Skull

Fig 24.24, p. 389 Early hominid (Proconsul) Early anthropoid (Aegyptopithecus) Tree shrew, a close relative of primates, has a pointy face and its eyes are on either side of its head. Early primate (Plesiadapis) Evolution of the Primate Skull

Fig 24.24a, p. 389 Evolution of the Primate Skull

5 Key Trends in Primate Evolution 3. Skeletal changes allowed upright standing and walking (bipedalism) Backbone keeps body aligned over feet Skull sits over the backbone bipedalism Standing and walking on two legs

Posture of Gorilla and Human Gorillas are knuckle- walkers Humans are bipedal

5 Key Trends in Primate Evolution 4. Hands developed increased dexterity Changes to bone and muscle in the hands allowed some primates to manipulate objects and use them as tools:

5 Key Trends in Primate Evolution 5. Braincase and brain increased in size and complexity Social behavior, extended parental care, and culture evolved in some hominid lineages culture Learned behavior patterns transmitted among members of a group and between generations

ANIMATION: Primate evolutionary tree To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

24.10 Emergence of Early Humans Fossils from central, eastern, and southern Africa show that hominids evolved rapidly in the Miocene through the Pliocene We still do not know how they are related

Early Hominids Fossils that may be hominids (ahelanthropus tchadensis) are about 6 million years old Ardipithecus ramidus was a hominid that lived 4.4 million years ago An bipedal hominid, Australopithecus afarensis, was walking in Africa about 3.9 million years ago

Lucy (Australopithecus afarensis)

Australopiths Australopiths (“southern apes”) include Australopithecus and Paranthropus species Australopithecus species were petite, with a small face and teeth australopiths Collection of now-extinct hominid lineages, some of which may be ancestral to humans

Early Humans The human lineage (Homo) arose by 2 million years ago with H. habilis as an early toolmaking species Most of the early known forms of Homo are from the East African Rift Valley humans Members of the genus Homo

Homo habilis and Australopiths

Stone Tools from Africa A crude chopper, more refined chopper, hand ax, and cleaver

Homo erectus Homo erectus (“upright man”) traditionally refers to African populations and to descendant populations who migrated into Europe and Asia H. erectus was taller and had a larger brain than H. habilis H. erectus probably had improved hunting skills, built fires, and cooked food

Hominid Skulls From Africa

ANIMATION: Primate skeletons To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

24.11 Emergence of Modern Humans Judging from the fossil record, the earliest members of the human lineage emerged about 2.5 million years ago, in the great East African Rift Valley Neandertals (H. neanderthalensis) and modern humans are relatives, but have distinct gene pools

Branchings of the Human Lineage Some populations of H. erectus differentiated into new species: H. neanderthalensis (Neandertals), H. floresiensis, and H. sapiens (modern humans) Compared to earlier hominids, H. sapiens had a higher, rounder skull, larger brain, and capacity for spoken language Neandertals vanished when H. sapiens entered the same regions

Recent Homo Species Whether H. floresiensis belongs in this genus is still debated Some think the fossils belong to H. sapiens individuals who had a disease or disorder

Fig 24.30, p. 392 Homo neanderthalensis Homo floresiensis Homo sapiens Recent Homo Species

Where Did Modern Humans Originate? Two major models agree that H. sapiens evolved from H. erectus but differ in details of where and how fast these events took place Both attempt to explain the distribution of H. erectus and H. sapiens fossils, as well as genetic differences among modern humans who live in different regions

Multiregional Model By the multiregional model, H. erectus populations in far-flung regions evolved into H. sapiens multiregional model Model that postulates H. sapiens populations in different regions evolved from H. erectus in those regions

Replacement Model The replacement model has modern humans evolving from H. erectus in Africa, then dispersing into regions already occupied by H. erectus and driving them to extinction replacement model Model for origin of H. sapiens; humans evolved in Africa, then migrated to different regions and replaced the other hominids that lived there Fossils support the replacement model

Two Models for Origin of H. sapiens

Fig 24.31, p. 392 Time Europe H. erectus A Multiregional model. H. sapiens slowly evolves from H. erectus in many regions. B Replacement model. H. sapiens rapidly evolves from one H. erectus population in Africa, then disperses and replaces H. erectus populations in all regions. H. sapiens Africa Asia Europe Africa Asia Two Models for Origin of H. sapiens

Leaving Home Fossils and genetic evidence allow scientists to trace human dispersal routes In their journey, humans overcame hardships, devised cultural means to survive inhospitable environments, modified habitats, and developed languages Cultural evolution is ongoing

Dispersal Routes for Homo sapiens Ice sheets and deserts prevailed about 60,000 years ago Fossil evidence for appearance of modern humans: Africa by 195,000 years ago Israel 100,000 years ago Australia 60,000 years ago China 50,000 years ago Europe 40,000 years ago North America 14,000 years ago

Dispersal Routes for Homo sapiens

Origins and Extinctions of Hominid Genera

Fig 24.33, p. 394 Time (millions of years ago) Paranthropus aethiopicus Homo erectus Homo habilis present Australopithecus garhi Australopithecus africanus Homo rudolfensis Australopithecus anamensis Australopithecus afarensis Paranthropus robustus Paranthropus boisei 41 Homo neanderthalensis Homo sapiens Homo floresiensis 32 Origins and Extinctions of Hominid Genera

Key Concepts Early Primates to Humans Primates have grasping hands with nails instead of claws Within the group, there is a trend toward increased brain size and manual dexterity, a flatter face, and upright posture Fossils provide information about lineages related to our species, which most likely evolved in Africa

Windows on the Past (revisited) Scientists often disagree over fossils When Homo floresiensis was found, some other scientists suggested that the fossils were remains of H. erectus or H. sapiens with a genetic or nutritional disorder Further study of existing fossils, a search for more fossils, and possibly DNA studies will help test competing hypotheses

ANIMATION: Genetic distance between human groups To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE