Being Human and Evolution

8/13/2019 Being Human and Evolution

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Being Human and Evolution


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Evolution

- Belief that species arose from others through along and gradual process of transformation ordescent modification.

Creationism- Explanation for the origin of speciesgiven in genesis: God created the species duringthe original six days of creation.

Theory- set of ideas formulated to explainsomething. The main value of a theory is topromote new understanding. A theory suggestspatterns, connections, and relationships that maybe confirmed by new research


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The theory of Evolution through Natural

selection (how evolution occurred)

- The process by which the forms most fit to

survive and reproduce in a given environment

do so greater numbers than others in the

same population; more than survival of the

fittest, natural selection is differentialreproductive success.


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Natural Selection operates when there isCompetition- on food, space between membersof population

Conditions of natural selection:

a. Variety-w/o variation, one kind of characteristiccould not be favored over the other

b. Heredity-offspring inherit traits from theirparents in some degree

c. Differential reproductive success- more adaptedreproduce over generations more than thosewho poorly adapted


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Independent Assortment and Recombination

-provide one of the main ways variety is producedin a given population

Independent assortment-Mendels law of; chromosomes are inherited

independently of one another (f1 gen.)

Recombination-following independent assortmentof chromosomes, new arrangements ofhereditary units are produced; creates new type


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Application:

-blood type (explain)

Mendelian Genetics studies the ways in which

chromosomes transmit genes across the

generations.


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Biochemical Genetics

-examines structure, functions and changes in DNA.

-how natural selection operates

Since, Mendels time scientists have learned aboutmutations- changes in the DNA molecules in which

genes and chromosomes are built.-DNA molecules make up genes and chromosomes which

are the basic hereditary units.

Chromosomes-basic genetic unit, made up of multiple

genesGenes- area in chromosome pairs which determines

wholly or partially a particular biological trait


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Biochemical Genetics

(Causes of Variety)

1. Cell division (cellular reproduction)

a. Mitosis- upon fertilization, zygote grows

rapidly

-ordinary cell division, DNA molecules copy

themselves creating two identical cells out of

one.

b. Meiosis-special process in which sex cells areproduced, (four cells are produced by one, with

half the genetic material of the original cell)


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2. Crossing over- before fertilization, pairedchromosomes intertwine as they duplicatethemselves.

a1,b1,c1,d1 a2,b2,c2,d2= a1,b1,c2,d2a2,b2,c1,d1

3.Mutation- most important source of variation

-simplest mutation results fromsubstitution of just one base in a triplet byanother.


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Population Genetics

(mechanism of genetic evolution)

1. Natural Selection

How natural selection operates?

a. Directional Selection- most adaptive will beselected again and again, except for changes in the

environmentb. Sexual selection- competition fro mates

Ex. Colors in birds

c. Stabilizing Selection- selective forces can also work

to maintain variety, by favoring a balancedpolymorphism, frequencies of two or more allele ofgenes remain constant from generation to generation


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2.Random Genetic drift-Change in gene

frequency brought results not from natural

selection but by chance, most evident in

small populations.

3. Gene Flow- exchange of genetic material

between populations of the same species

through direct or indirect interbreeding.


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Human Variation and Adaptation

2 ways on explaining biological diversity:

1. Racial classification

-attempt to assign humans to discrete categories

based on common ancestry. A race is supposedto reflect shared genetic material inherited by acommon ancestor but early scholars usedphenotypical traits for racial classification

2.Current explanatory approachexplanation orunderstanding on the differences rather thancategorization


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Race as discredited concept in Biology

Phenotypical traits for racial classification are

skin color, height, hair type, skull form and a

lot more. There are three main groups of races

called the tripartite scheme:

a. Caucasoid

b. Mongoloid

c. Negroid


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Problem with Race

Phenotypical characteristics dont necessarily

have a genetic basis

When combining physical traits, the number

of combinations is very large.

Race is a product of colonial empire,

embedded with meanings such as slavery,

inequality


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From categorization to explanation

Explaining skin color:

The epidermis manufactures chemical

substance called melanin, the primary

determinant of skin color.

Melanin protects the human body by

screening out ultraviolet radiation.

Light skin is advantage in cloudy north but

disadvantage in the sunny tropics


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Human biological Adaptation

1.Genes and Diseases

-the prevalence of different diseases favors

some genetic traits in which natural selection

operates, this changes the gene frequencies

among population.

Some of these diseases are Malaria and

smallpox ( mostly common on blood type A or

AB)


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2.Facial Features

-long noses are adaptive in arid areas because

membranes and blood vessels inside the nose

moisten the air as it is breathed in.

-long noses are also adaptive in cold areas

because blood vessels warm the air as it is

breathed in

(Thomsons nose rule)


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Teeth

-Native Australians have larger dentition becausethey their food is accompanied with sand and

grit.3. Size and Body Build

Bergmanns rule- the smaller of two bodies similarin shape has more surface area per unit of weight

and therefore can dissipate heat more efficiently;hence, large bodies tend to be found in colderareas and small bodies in warmer areas


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Allens rule- relative size of protruding body partstends to increase in warmer areas

4. Lactose Tolerance

-milk contains sugar called lactose. The digestion ofmilk depends on enzyme called lactase. About 90percent of N. European are lactose tolerant and80 percent of African population as well. These

populations are traditionally herders. For thosewho were not herders, like Eskimos, Asians, theycant digest lactose.


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Humans in zoological taxonomyTaxon Scientific Name Name(English)

Kingdom Animalia Animals

Phylum Chordata Chordates

Subphylum Vertebrates Vertebrates

Class Mammalia Mammals

Infraclass Eutheria EutheriansOrder Primates Primates

Suborder Anthropoidea Anthropoids

Infraorder Catarrhini Catarrhines

Superfamily Hominoidea Hominoids

Family Hominidae Hominids

Tribe Hominini Hominins

Genus Homo Humans

Species Homo sapiens Recent humans

Subspecies Homo sapiens sapiens Anatomically modernhumans


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The Primates-Human beings belong to the Order primates in the zoological

taxonomy1. Prosimians

2. Anthropoids

2.1 Monkeys

a. New World Monkeysb. Old World Monkeys

2.2 Apes

i. Gibbons

ii. Orangutans

iii. Gorillas

iv. Chimpanzees

v. Bonobos

2.3 Humans


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Primate Tendencies

1. Grasping- primates have five-digited feetand handssuited for grasping

-bipedal, opposable thumbs

2. Smell to sight-monkeys and apes have excellent

stereoscopic and color vision3. Nose to hand- touch

4. Brain complexity- primates ratio of brain to weight hadexceeded most of mammals

5.Parental investment- give birth to only single offspring6. Sociability


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Living Primates

Prosimians Anthropoids

Lemurs, Tarsiers N.world monkeys O. world

(Platyrrhines) primates(Catarrhines)

Apes &Humans(Hominoids)


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The Apes And Human

(Hominoids) Lesser Apes

-Gibbons and Siamangs

Greater Apes

-Chimpanzees, Orangutans, Gorillas, and Humans

Gibbons and Siamangs-most agile

-relatively smaller (gibbons, 11 to 15 pounds) in size, theirrelative siamangs are much larger (


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Orangutans

-sexual dimorphism (males, weighs 2x as females,up to 200 pounds)

-fruit eaters, arboreal-solitary lives

Gorillas

-eat part of plants, fruits are part of their diet

-largest among surviving apes (male-450 pounds)-live in groups consisting with dominant male

(silverback)


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Chimpanzees

-common chimpanzee and the bonobo

-most sociable

-bonobos are more gracious than commonchimpanzees and centered on females (no/lesssexual dimorphism)

-both are arboreal and terrestial

-males weighs a little more than 100 pounds, andfemales somewhat less

-omnivorous


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Variation Among Primates

Body Size

-diurnal or nocturnal

-arboreal or terrestrial

- Diet (species that eat mostly leaves are larger)

Relative Brain Size

Ratio of body size to brain size

-fruit eaters have relatively larger brain

-fruit (more nutrients, glucose for memory)


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Group size

Nocturnal- solitary/ in pairs

Diurnal-groups

Except for some reasons like scarcity or

resources and adaptation to heavy predation


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Similarities Between Humans and Non

Human Primates

Learning

Tools

Predation and Hunting

Aggression and Resources

Distinctly Human

Sharing and Cooperation

Mating and Kinship( marriage and exogamy)-produce allies and lifelong ties


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Distinctly Human Traits

Physical Traits

-only human consistently walk erect (fully bipedal)

-greater length and dexterity of human thumb

(power grip, precision grip)

-the human brain is large and complex, particularly

the cerebral cortex (center of speech and higher

mental activities)

-human teeth (omnivorous diet)


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Tool making

-only humans are habitual toolmakers; they use

tools and make another

Language

-spoken, symbolic language

Other traits-only humans have division of labor


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The first Hominid

- Ardipithecus ramidus, the first bipedal ape?Australopeticenes (gracile, robust)

-Australopithecus Anamensis

4.2 to 3. 9 (m.y.a)

-A. Afarensis

3.8 to 3.0 (m.ya), 77lb/35 kg., 430 cc

-A. Africanus

3 to 2.?, 79lb/36 kg., 490 cc

-A. robustus

2.? To 1.? (m.y.a) 81 kg/37kg, 540 cc

-A. boisei

2.6? To 1.2 m.y.a 86/39 kg., 490 cc


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The first Hominids

Theory of Bipedalism

- To see predators and potential prey while

moving on tall grass

- Favored travelling on two legged for long

distance

- Use of tools


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Genus Homo

Homo- the genus that contains the modern humanspecies

-had a brain one third larger than the

autralopithecines- One consequence of brain expansion was the

lessening of maturity at birth

-childhood dependency made it possible for home

bases that encouraged the development oflearned and shared behavior (evolution ofculture)


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Increased brain size of the Homo wasfavored by natural selection because theyhave more motor and conceptual skills to be

better toolmakers. Thus, more sophisticatedtools developed altogether.

-larger brain was favored for hunting, language.

Therefore whatever reasons, bigger brainsprovided humans for an expanded capacity forculture.


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Homo habilis- latin able, 600 to 700 cc (630-640cc)

-showed the first evidence of stone tool use and

manufacture based on a simple stone choppercalled Oldowan made by hammering one stonewith another top produce a cutting edge.

Oldowan tools- earliest known stone tool

technology which was associated by the Homohabilis and named for the location of itsdiscovery, Olduvai Gorge in E. africa


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-Homo erectus- looks more human, moresophisticated tools, straighter edges, 1000 cc

-tools that can batter, and crush, and pulp coarse

vegetation that reduces chewing demandsAcheulian- the stone tool technology associated

with homo erectus, bifacial implements,

-apparently used fire and constructed rudimentary

shelters

-cooperative hunting (language?)

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Being Human and Evolution