The Descent of ManThe Descent of Man

MHS ScienceMHS Science

The History of Biological The History of Biological SciencesSciences

A Little Stroll Through An Odd Assortment of A Little Stroll Through An Odd Assortment of Ideas, Facts, Theories, and Debates Concerning Ideas, Facts, Theories, and Debates Concerning

The Descent of ManThe Descent of Man

ATTENTION!!ATTENTION!!!!

This is NOT a discussion on evolution and the scientists associated with it. It is simply some of their ideas applied to our species.

Charles Charles DarwinDarwin

Alfred Russel Alfred Russel WallaceWallace

LinnaeusLinnaeus

Thomas Thomas HuxleyHuxley

BuffonBuffon

LamarckLamarck

Georges Cuvier

Charles Charles LyellLyell

New discoveries are always just around the New discoveries are always just around the corner. As members of an educated public, corner. As members of an educated public,

you will understand and perhaps even you will understand and perhaps even participate in the debate and just as participate in the debate and just as

important, the development of a more important, the development of a more complete comprehension of complete comprehension of Homo sapiensHomo sapiens, , the animal, as well as the animal, as well as Homo sapiens,Homo sapiens, the the

human being.human being.

ONTOGENY RECAPITULATES PHYLOGENY

The history of the development of an individual organism

Ontogeny

Phylogeny

The evolutionary history of a species; evolutionary relationships of organisms; a “family tree”

The Mammalian Brain•Large and versatile

•Rely less on genetically programmed instinct

•Adjust more readily to environment - basing behaviour on experience and learning

•The cerebrum (learning center and region of conscious thought) relatively larger

•Corpus callosum has been added

Look at me…I’m a mammal

Mammalian Points of Mammalian Points of InterestInterestFossil records indicate mammals arose from therapsidstherapsids (197 to 225 million years ago)Three (3) types of mammals:

Placental (uterine embryonic development)

Marsupials (birth immature young - pouch

development)Monotremes (hairy egg layers)

Tree shrewsTree shrews

TarsiersTarsiers

LemursLemurs

Loris and Loris and PottoPotto

Monkeys - Apes - Monkeys - Apes - HominidsHominids

New WorldNew World Old WorldOld World

CeboideaCeboidea (prehensile tail)

CercopithecoideCercopithecoideaa

Gibbons, Gibbons, Orangutans, Orangutans, Gorillas, Gorillas, Chimpanzees,Chimpanzees,

HominoideaHominoidea

LemurLemur SifikasSifikas

Chimpanzee

Gorilla

Orangutan

Chimpanzee Chimpanzee SkeletonSkeleton

Monkey SkeletonMonkey Skeleton

Skull + DentitionSkull + Dentition

Long Bones - Long Bones - RobustRobust

Pelvic GirdlePelvic Girdle

Torso - Torso - Rib CageRib Cage

Femur Femur articulationarticulation

Hands and FeetHands and Feet

Skeletal Close-Skeletal Close-Up...Up...From trees to From trees to terrestrialterrestrial

Quadruped to BipedQuadruped to Biped

About 4.4 millions years ago, a different type of primate emerged. Paleontologists classify the first bipedal primates as hominids.

These first hominids had not yet developed the large brain, teeth structure, and skeletal features we identify as Homo. Instead, they predate, and sometimes overlap the first Homo species.

They are known as the Australopithecines.Australopithecines.

AustralopithecinAustralopithecinesesGracile Australopithecines Robust Australopithecines

Australophithecus afarensis

Australopithecus africanus

Australopithecus robustusAustralopithecus boisei

Both gracile australopithecines were:1. Small in stature (1 - 1.5 meters)2. Similar brain size/cranial capacity (400 - 500 ml)3. Light body structures

A. afarensis

More ape-like

Predates A. africanus by 1.5 my

Bi/Quadrupedal

A. africanus

Bipedal - musculature is similar to baboons

Found before A. afarensis

I am “Lucy”

And they callme “Taung

child”.

It is not known how these species directly affected It is not known how these species directly affected human evolution. However, there are many theories:human evolution. However, there are many theories:

A. afarensis

A. africanus

Homo

A. boisei

A. robustus

A. afarensis

A. afarensis

A. boisei

A. africanus

A. robustus

Homo

A. africanus

Common ancestor

Homo

Both robust

At around two million years ago...

Homo habilis(Evolutionary and technological breakthroughs)

Cranial capacity 600 - 800 ml

First stone tools developed

Habilis means handy-man

.

At around one million years ago...

Homo erectus(Evolutionary, technological and cultural adaptations)

Cranial capacity 750 - 1250 ml and foreheads begin to develop as a result of a growing frontal lobe (foresight - reasoning - concentration)

H. erectus and H. sapiens practically identical below the neck.

Hand ax, weapons, big-game hunting and the use of fire

Habitual erect posture and efficient bipedal gait

Nothing..

At around 75 to 30 thousand years ago...

Homo sapiens neanderthalensis

Homo sapiens sapiens

Cranial capacity 1250 - 1750 ml (Neandertal) - sloping forehead

1200 - 1600 ml (Modern humans)

Larger Birth canal and wider pelvic width - longer gestation?

Bones considerably more robust

It is far from easy to put these fellas in their place

No Neandertal traits fall totally outside the variation range of modern humans.

Neandertal variations:

Cranial Capacities - A Cranial Capacities - A ComparisonComparison

A Side ViewA Side ViewNote: Note: Temporal Temporal bonebone

Frontal bone Frontal bone (slope)(slope)

Occipital boneOccipital bone

Maxilla and Maxilla and MandibleMandible

A. africanus

H. habilis

H. erectus

H. sapiens

A Frontal ViewA Frontal ViewNote: Note: Frontal boneFrontal bone

Brow ridgeBrow ridge

Zygomatic archZygomatic arch

MaxillaMaxilla

A widely accepted theory (to A widely accepted theory (to date)date)

Based on:Based on:Dentition

Skull anatomy

Fossil location

Mitochondrial DNA

Long bone analysis

Pelvic girdle

Radioactive dating

Evolution: The Human Evolution: The Human AdventureAdventure

Life 3.5 billion years ago

Fossil vertebrate record 500 million years

Placental mammal radiation to the beginnings of the primate order more than 60 m.y.a.

New/Old World divergence 40 m.y.a.

First hominoid 20 m.y.a.

Disputed: 10 - 5 m.y.a. first hominid (human family)

Australopithecus afarensis 5 m.y.a.

The genus Homo emerging 2 m.y.a.

Homo erectus 1 m.y.a.

Homo sapiens sapiens 100 000 - 40 000 years ago

Hominid evolutionary development has created Hominid evolutionary development has created Homo sapiensHomo sapiens, an animal with behavioural , an animal with behavioural flexibility. But unlike any other organism on this flexibility. But unlike any other organism on this planet we can infinitely mold our own behaviour planet we can infinitely mold our own behaviour through exercise of our own uniquely human through exercise of our own uniquely human creativity.creativity.Does this mean we have left the realm of biological Does this mean we have left the realm of biological evolution?evolution?

No, but our profound ability to modify our No, but our profound ability to modify our environments has outdistanced our biological environments has outdistanced our biological capacity to respond.capacity to respond.

How then can we be expected to How then can we be expected to cope with the new biological cope with the new biological

pressures of the modern pressures of the modern technological world?technological world?

Clearly, the biggest dangers are the cultural Clearly, the biggest dangers are the cultural ones we have created for ourselves: ones we have created for ourselves: POLLUTION, OVERCROWDING, WAR, POLLUTION, OVERCROWDING, WAR, RESOURCE MISMANAGEMENT, and so forth.RESOURCE MISMANAGEMENT, and so forth.

Equally as clear, the only viable answers Equally as clear, the only viable answers are also cultural ones.are also cultural ones.

As human beings, we possess the As human beings, we possess the capability to remake the world - for capability to remake the world - for

better or worse.better or worse.

The choices are ours.