Introduction to Evolution Chris Scott, Ph.D.

Evolution and Diversity of Vertebrates

ANCESTRALDEUTEROSTOME

Notochord

Commonancestor ofchordates

Head

Vertebral column

Jaws, mineralized skeleton

Lungs or lung derivatives

Lobed fins

Limbs with digits

Amniotic egg

Milk

Echinodermata

Cephalochordata

Urochordata

Myxini

Petromyzontida

Chondrichthyes

Actinopterygii

Actinistia

Dipnoi

Amphibia

Reptilia

Mammalia

Ch

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ates

Cra

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Verteb

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Lo

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Am

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Derived Characters of Chordates

• All chordates share a set of derived characters

• Some species have some of these traits only during embryonic development

• Four key characters of chordates:

1. Notochord

2. Dorsal, hollow nerve cord

3. Pharyngeal slits or clefts

4. Muscular, post-anal tail

Musclesegments

Notochord

Dorsal,hollow

nerve cord

Muscular,post-anal tail

Pharyngealslits or clefts

Anus

Mouth

Flat skull

Eyes on top of skull

Head

Neck

Shoulder bonesRibs

Scales

Fin Fin skeleton

Elbow

Radius

Humerus

Ulna

“Wrist”

ScalesFinsGills andlungs

NeckRibsFin skeletonFlat skullEyes on topof skull

TetrapodCharacters

FishCharacters

Tiktaalik the “fishapod"

• Tiktaalik could most likely prop itself on its fins, but not walk

• The first tetrapods appeared 365 million 365 million years ago

Cephalochordata

Urochordata

Myxini

Petromyzontida

Chondrichthyes

Actinopterygii

Actinistia

Dipnoi

AmphibiaReptilia

Mammalia

Mammals have:

– Mammary glands, which produce milk– Hair – A high metabolic rate, due to endothermy– A larger brain than other vertebrates of

equivalent size– Differentiated teeth

Mammals are amniotes that have hair and produce milk

Early Evolution of Mammals

Early Evolution of Mammals

• Mammals evolved from reptilian synapsidssynapsids• These reptiles arose during the Pennsylvanian Period (310 to 275 million These reptiles arose during the Pennsylvanian Period (310 to 275 million

years ago). A branch of the synapsids called the therapsids appeared by years ago). A branch of the synapsids called the therapsids appeared by the middle of the Permian Period (275 to 225 million years ago). It was over the middle of the Permian Period (275 to 225 million years ago). It was over millions of years that some of these therapsids would evolve many features millions of years that some of these therapsids would evolve many features that would later be associated with mammals.that would later be associated with mammals.

Hominins and the Evolution of Humans

Primates

• The mammalian order Primates includes lemurs, tarsiers, monkeys, and apes

• Humans are members of the ape groupape group

• Most primates have hands and feet adapted for grasping, and flat nails

Derived Characters of Primates

• Other derived characters of primates – A large brain and short jaws

– Forward-looking eyes close together on the face, providing depth perception

– Complex social behavior and parental care

– A fully opposable thumb (in monkeys and apes)

• There are three main groups of living primates:

I. Lemurs, lorises, and pottos

II. Tarsiers

III. Anthropoids (monkeys and apes, including humans)

Living Primates

• The first monkeys evolved in the Old World (Africa and Asia)

• In the New World (South America), monkeys first appeared roughly 25 million years ago

• New World and Old World monkeys underwent separate adaptive radiations during their many millions of years of separation

(b) Old World monkey: macaque(a) New World monkey:spider monkey

• The other group of anthropoids consists of primates informally called apes

• This group includes gibbons, orangutans, gorillas, chimpanzees, bonobos, and humanshumans

• Apes diverged from Old World monkeys Old World monkeys about 20–25 million years ago

Apes

(a) Gibbon(b) Orangutan

(c) Gorilla

(d) Chimpanzees

(e) Bonobos

(d) Chimpanzees

ANCESTRALPRIMATE

Time (millions of years ago)

60 50 40 30 20 10 0

Lemurs, lorises,and bush babies

Tarsiers

New World monkeys

Old World monkeys

Gibbons

Orangutans

Gorillas

Chimpanzeesand bonobos

Humans

An

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ids

Last Common Ancestor for Humans and Chimpanzees: 7 Million years ago

What does Hominin mean?

• Hominin is a creature that paleoanthropologists have agreed is human or a human ancestor

• Hominins include all of the Homo species (Homo sapiens, H. erectus , H. heidelbergensis), all of the Australopithecines and other ancient forms like Paranthropus and Ardipithecus

Hominin Timeline

Evidence of Bipedalism from the fossilized skull alone

Comparison of Hip and Foot Bones

longer ape pelvis is adapted for quadrupedal locomotion

Evidence that Hominins walked upright 3.5 million years ago

Footprints found near Lake Turkana, Kenya, show that human foot shape and gait had been achieved 1.5 million years ago

SCIENCE, VOL 323, ISSUE 5918,  pages 1197-1201 (Feb. 27, 2009) Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya

SCIENCE, VOL 323, ISSUE 5918,  pages 1197-1201 (Feb. 27, 2009) Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya 

• Hominin comprises the genera Homo, and the two species of the genus Pan (the Common Chimpanzee and the Bonobo), their ancestors, and the extinct lineages of their common ancestor

Hominin

Ardipithecus ramidus

Between 1993 and 2003 bones of numerous Ardipithecus ramidus specimens were found in Ethiopia

Ardipithecus ramidus

October 1, 2009, paleontologists formally announced the discovery of the relatively complete A. ramidus fossil skeleton first unearthed in 1994. The fossil is the remains, dated 4.4 million years old, of a small-brained 110 lb, 3 foot 11 inch female, nicknamed "Ardi", and includes most of the skull and teeth, as well as the pelvis, hands, and feet.

Researchers infer from the form of her pelvis and limbs and the presence of her abductable hallux, that she was a facultative biped: bipedal when moving on the ground, but quadrupedal when moving about in tree branches.Based on enamal thickness the teeth suggest she was an omnivore – her dental makeup is more generalized than those of modern apes

Ardipithecus ramidus

http://www.sciencemag.org/content/326/5949/60.2.full

Youtube version

Visual Reconstruction of Ardi movement

Australopithecus afarensis

Nickname: Lucy's speciesWhere Lived: Eastern Africa (Ethiopia, Kenya, Tanzania)When Lived: Between about 3.85 and 2.95 million years ago (900,000 thousand years!)Features: 4 foot 11 inches; 100 lbs; combination of bipedal and tree climbing abilities; small brain; dental structure of omniovore

Homo habilis (handy man)

Early Homo

• The earliest fossils placed in our genus Homo are those of Homo habilis, ranging in age from about 2.4 to 1.6 million years

• Stone tools have been found with H. habilis, giving this species its name, which means “handy man”

Homo habilis (handy man) • Earliest known species of the hominin group that has the Homo genus• Lived from approximately 2.33 to 1.4 million years ago• Some fossils of H. habilis are found with shaped stone toolsshaped stone tools• Homo habilis has often been thought to be the ancestor of the more

gracile and sophisticated Homo ergaster, which in turn gave rise to the more human-appearing species, Homo erectus.

• In 2000 a relatively late 1.44 million-year-old Homo habilis and a relatively early 1.55 million-year-old Homo erectus from the same area of northern Kenya challenged the conventional view that these species evolved one after the other

• Instead, this evidence - along with other fossils - demonstrate that they co-existed in Eastern Africa for almost half a million years!half a million years!

1.7 MY old Fossil of Homo ergaster

Homo ergaster characteristics

• Fossils from 1.9 to 1.5 MYA show a new stage of hominin development

• H. ergaster had a bigger brain than H. habilus

• H. ergaster had long slender legs with hip structure adapter for walking

• H. ergaster fingers were shorter and straighter, implying lack of tree climbing

• Sexual diamorphism is reduced

• Tooth structure implying more meat eating

Homo erectus

Homo erectus (upright man) is an extinct species of hominid that lived about 1.9 million to 143,000 years ago (1.75 million years!!!1.75 million years!!!)

The species originated in Africa and spread as far as India, China and Java.

Homo erectus, female. Reconstruction based on ER 3733 by John Gurche, front view

Homo erectus

Features: average height is 5 foot 9 inches, weight was about 150 lbs; oldest known early humans to have possessed modern human-like body proportions with relatively elongated legs and shorter arms compared to the size of the torso. These features are considered adaptations to a life lived on the ground, indicating the loss of earlier tree-climbing adaptations, with the ability to walk and possibly run long distances. Compared with earlier fossil humans, note the expanded braincase relative to the size of the face. The appearance of Homo erectus in the fossil record is often associated with the earliest handaxes, the first major innovation in stone tool technology.

Homo erectus

Range: Generally considered to have been the first species to have expanded beyond Africa, Homo erectus is considered a highly variable species, spread over two continents (it's not certain whether it reached Europe), and possibly the longest lived early human species - about nine times as long as our own species, Homo sapiens, has been around!

Homo erectus

Homo heidelbergensis

700,000 – 200,000; first early human species to live in colder climates, it was the first early human species to routinely hunt large animals. This early human also broke new ground; it was the first species to build shelters—creating simple dwellings out of wood and rock.

Homo heidelbergensis

•Comparison of Comparison of NeanderthalNeanderthal and and Homo sapiens Homo sapiens DNA DNA suggests that the two lineages diverged from a suggests that the two lineages diverged from a common ancestorcommon ancestor, most likely , most likely Homo heidelbergensisHomo heidelbergensis, , sometime between 350,000 and 400,000 years ago sometime between 350,000 and 400,000 years ago – – with the European branch leading to with the European branch leading to H. H. neanderthalensisneanderthalensis and the African branch to  and the African branch to H. H. sapienssapiens

Homo neanderthalensis

Homo neanderthalensis was a living species from at least 400,000 to 30,000 million years ago

Homo neanderthalensis• The ancestors of Neanderthals left Africa about 400,000 to 800,000 years ago

• Neanderthals evolved over the millennia mostly in what are now France, Spain, Germany and Russia

• They were thick-boned with a larger brain (comparable to humans, stronger than humans, they buried their dead, and they made hunting tools

• Neanderthals went extinct, or were simply absorbed into the modern human population, about 30,000 years ago

Homo sapiens: Out of Africa• Our species is called Homo sapiens

• During a time of dramatic climate change 200,000 years ago, Homo sapiens evolved in Africa

• Like other early humans that were living at this time, Homo sapiens gathered and hunted food, and evolved behaviors that helped them respond to the challenges of survival in unstable environments

Homo sapiensCompared to other members of the genus Homo, Homos sapiens have:

1.1.A lighter build of their skeletonsA lighter build of their skeletons

2.2.Large brainsLarge brains

3.3.A thin-walled, high vaulted skull A thin-walled, high vaulted skull

4.4.A flat and near vertical foreheadA flat and near vertical forehead

5.5.Much less (if any) heavy brow ridges Much less (if any) heavy brow ridges

6.6.Smaller nosesSmaller noses

7.7.Less heavily developed jawsLess heavily developed jaws

8.8.Smaller teethSmaller teeth

Homo sapiens and Homo neanderthalensis

• The earliest known Homo sapiens in Europe lived in a southern Italian cave 45,000 years ago

• Homo sapiens were also in what is now the U.K. about 44,000 years ago

• Neanderthal fossils have been found in Europe and Asia as recently as 28,000 years ago

• These studies show that Homo sapiens quickly spread over Europe and coexisted with Neanderthals

Homo sapiens and Homo neanderthalensis• In May 2010 (Science magazine) a draft sequence of the Neanderthal genome was published

• Genomic comparison confirmed Homo sapiens and Homo neanderthalensis interbred

• Most, if not all, of the interbreeding took place in the Middle East, while modern humans were migrating out of Africa and spreading to other regions

• If your heritage is non-African, you are part Neanderthal!If your heritage is non-African, you are part Neanderthal!

Homo sapiens and Homo neanderthalensis

• The Homo sapiens/Neanderthal combination likely enabled interbred Homo sapiens to survive in harsh, cold regions that Neanderthals previously had adapted to

• Variability is very important for long-term survival of a species -- every addition to the Variability is very important for long-term survival of a species -- every addition to the genome can be enrichinggenome can be enriching

•Humans first arrived in the New World (North and South America) sometime before 15,00015,000 years ago by travelling across the Alaska-Russia land bridge

•In 2004, 18,000-year-old fossils were found in Indonesia, and a new small hominin was named: Homo floresiensis

A timeline for some selected hominin species

• Homo sapiens were the first animal group to show evidence of symbolic and sophisticated thought

• Chimpanzees regularly crack open hard-shell seeds and nuts with a stone hammer against a stone or wooden anvil; and they'll carry the appropriate rocks over a good fraction of a kilometer for the purpose. 

• A chimp breaks off a long grass stalk or a reed so she may use it later, hundreds of meters away, more than an hour in the future, to lure delectable termites out of a log or termite mound.

Gorilla using a stick to test water depth

In 2002, a 77,000-year-old artistic carving was found in South Africa

Timeline 

•Approximate age of the Universe: 14 billion years................................ 14,000,000,000•Approximate age of the Earth: 4.5 billion years........................................4,500,000,000•Approximate age of life on this planet: 3.5 billion years....................3,500,000,000•First tetrapods (Tiktaalik, the first “fishapod”)..............................................365,000,000•Permian Great Extinction.........................................................................245,000,000•Evolution of the first mammals and.............................................................240,000,000•K-T Great Extinction (end of the dinosaurs).............................................65,000,000•Earliest fossil evidence of the first hominin (Sahelanthropus tchadensis).......6,500,000•Age of “Ardi” (Ardipithecus ramidus) fossils....................................................4,400,000•Earliest fossils of the genus Homo (Homo habilus, “handy man”)...................2,400,000•Approximate age of our species Homo sapiens.................................................200,000•Approximate age of the first human civilizations: less than 8,000 years ago..........8,000•Approximate age of oldest discovered book*: .......................................................4,000•Start of mass produced books using the Gutenberg press (~1440 AD)....................572•Number of years the iPad has been available to the public...........................................2

* The Epic of Gilgamesh is an epic poem recorded on 12 clay tablets from Ancient Mesopotamia (now Iraq)