Human Evolution Exam 2

Cline

A gradual change in some phenotypic characteristics from one population to the next

how related are homo sapiens to each other?

Incredibly related (99.9%) to every other human on the planet due to continuous gene flow.

First trimester

Fertilized ovum multiples into millions of cells eventual emergence of tissue types, organs and physiological systems. Most vulnerable environmental period of life.

Second Trimester

Fetus mostly grows longer.

Third Trimester

Rapid weight growth and organ development

Teratogens

agents that can inflict disruption insults, and deformities during development.

Veratrum californicum

produces an anti-herbivory chemical that blocks Shh signaling

SHH

also known as sonic hedgehog syndrome it divides optic field by suppressing Pax6 expression in the center of the neural tube.

Growth velocity

each of the postnatal periods has a different growth velocity

Human dental formula

2 incisors -1 canine -2 molars -3 premolars

Motor skills development

walking and running generally develop in first two years.

Cognitive abilities early development

rapid growth rate of the brain

when does permanent dentition begin?

6 years old

Deciduous

baby teeth

Diphyodont

two sets of teeth in our lives.

Dental Attrition

Wear and tear on teeth

Brain Development

Fetal brain is relatively smooth. By 40 weeks, you develop the wrinkles you will have for the rest of your life.

when has the human brain reached full size and nearly complete development

by 6 years old

when are the major regions of the brain differentiated but not fully developed

11 weeks

Ape brain development

flatlines after age 2

Human Brain Development

Humans continue absolute growth during childhood

Rhesus Monkey brain maturity by size at birth

48-68% of adult size

Chimpanzee brain maturity by size at birth

36-46% of adult size

Human brain maturity by size at birth

25-29%

How does poor sanitation in emerging cities impact height?

poor sanitation causes average heights to decrease.

Epiphysis

Ends of bones, separate growth. Common in long bones.

Diaphysis

Shaft or central portion of the (long) bone

Growth plate

Areas of growth between bones. Filled with cartilage then eventually filled with bone

do bones have veins inside of them?

Yes, bones are very vascular and cartilage is relatively avascular

what happens when exposed to low atmosphere pressure

Reduces the number of oxygen molecules, hypoxia becomes an issue

Hypoxia

When body tissues receive insufficient amounts of oxygen.

affects of hypoxia

leads to motion sickness, headaches, nausea, loss of appetite, fatigue, and breathlessness during physical activity; 8,000 ft during rest). (severity and risks increase as a person moves higher)

High altitude and bone growth

can impede normal bone growth as it is strongly affected by the environment (nutrition -\[not much grows on mountains\] and general health.)

Peruvian Andes

\-Larger chest cavities than low altitude people

\- Restricted growth so generally shorter

\- Larger lungs and better lung function

Tibetan women

Selection: Alleles for high oxygen saturation in their hemoglobin

\- More oxygen = better survival = better reproduction = Natural selection

\- Much more resilient to hypoxic impacts

Regarding Growth and Development

Prenatal and postnatal males appear to be more sensitive to environmental insult than females

Bergmann's Rule

Principle that animal size is often heat-related.

\
\- Animals adapted to hot environments tend to have less body mass.

\
\- Animals adapted to cold environments tend to have greater body mass

endotherms

Warm-blooded animals. we produce internal heat simply by living

Hyperthermia

Body temp is higher than normal range, loss of function and death.

Vasodilation

Increase blood vessel diameter near the body's surface. This is a way of getting more blood to the surface so it can cool before going back to the core of the body.

Sweating

a physiological response to release heat. Humans have an abundance of eccrine glands to produce sweat.

Allen's Rule

Principle that some animal's limb lengths are heat related.

\- arms/legs tend to be longer in hot environments

\- arms/legs tend to be shorter in cold environments

Climate Adaptation

Vasoconstriction

Shivering

Elevated BMR

Clothing and shelter

Vasoconstriction

Decrease blood vessel diameter. This increases blood flow back to the core of the body to produce more heat.

where is darker skin seen?

nearer to the equator and in high elevations

where is lighter skin seen?

away form the equator and in lower elevations

What do melanocytes produce

a pigment called melanin

Eumelanin

Browns to black skin tone, variations in this largely dictate skin/hair pigmentation/coloration

Pheomelanin

Pink to red hues (lips, nipples, hair, etc.)

Neuromelanin

Found in brain. Function unresolved.

Folate

Prevents a large number of neural tube defects (NTD). Important in spermatogenesis, reduce heart defects in fetus, reduce stroke risk, DNA synthesis and repair, etc.

Vitamin D

a hormone that increases calcium absorption of the small intestine and thus makes calcium available for building bones.

Drawbacks for dark skin away from equator

not enough vitamin D synthesis because low light conditions and so much melanin that synthesis becomes difficult

\
Modern Treatment is Vitamin D supplementation

Drawbacks or light skin near the equator

higher skin cancer risk due to especially high UV. Lose too much folate because skin is not dark enough to protect it.

\
modern Treatment: Sunscreen/covered skin; Folate supplementation.

Primates

a group of closely related and arboreally adapted mammals that live largely in the tropics. they display remarkable dietary plasticity and parental investment

Strepsirhines

Lemurs, lorises, galagos, pottos.

\- They have a post-orbital bar

\- Many are nocturnal and some diurnal

\- Some have nail and tooth adaptations for grooming

\- Mostly see in black and white with the tapetum lucidum in the eye (allows for night vision)

\- retain strong olfaction

Postorbital septum, bar, and process

P.O. Septum: Bony cup, fully closed

P.O. Bar: Partially closed

P.O Process: Incomplete closure

Lemurs

Found in Madagascar

21% of all primate Genera

Most are highly social

Dominant female

Diet of leaves and fruits

Some diurnal, some nocturnal

Lorises

Found in SE Asia, Sri Lanka, Africa

Generally nocturnal

Lack external tail

Primarily insectivores

Galagos

\- Found in Africa (large distribution)

\- Nocturnal

\- Primarily insectivorous... but also fruit and small animals

\- Common social group: female and offspring

\- Excellent jumpers

Pottos

Found in West/Central Africa

Nocturnal

Nearly exclusively arboreal

Diet=fruit, gums, insects

Haplorhines

Includes NWM, OWM, Apes, and Humans

\
\- Larger brains

\- Greater sexual dimorphism

\- Fewer teeth

\- Orbit = full bony septum aka "Post-orbtial septum"

\- Fully convergent eyes

\- Many have color vision, Most diurnal

\- lack a tapetum lucidum in the eye.

Dentition of primates

Most Strepsirhhines - 2.1.3.3

NWM: 2.1.3.3

OWM, Apes, and Humans: 2.1.2.3

Primitive Trait

Trait shared due to its presence in a common ancestor

Derived Trait

Derived Trait

Platyrrhines aka New World Monkeys

\- Found in the Americas (central and south)

\- Some have prehensile tails

\- 2.1.3.3 or 2.1.3.2. dental formula. 1 more premolar than we have

\- Folivory (leaf diet), frugivory (fruit diet), and insectivory.

Cercopithecoids: Old World Monkeys

\- Found across the "old world"

\- Approx. 22+ Genera 132+ species

\- Colobines ("leaf eating"\*, arboreal\*)

\- Colobus, Langurs, Proboscis

\- "Sacculated Stomachs", reduced or absent thumbs.

\
\- Cercopithecines (cheek pouch, monkeys, arboreal and terrestrial)

\- Mandrills, baboons, vervets, etc.

\- "Ischial Callosities"

\- 2.1.2.3 dental formula

Catarrhines are divided into 2 superfamilies

Cercopithecoids, Hominoids

Cheek pouches

found in Cercopithecines. They are hypothesized to function to

\
1) Reduce Competition with members of their own species

2) Predator Risk Avoidance

3) Storing Food, Resource Distribution.

The tapetum lucidum

an extra layer of tissue in the eyes of some vertebrates. Functions to provide the light-sensitive retinal cells with a second opportunity for photon-photoreceptor stimulation, thereby enhancing visual sensitivity at low light levels. (causes eye shine in photos)

Two types of primate teeth

Y-5 (Humans, Orangutans, Chimpanzee, Gibbons), Bilophodont (Colobus Monkey)

Brachiation

A form of locomotion where an animal can fling themselves from tree limb to tree limb. Gibbons and Siamangs have long arms and curved fingers that help them do this.

which ape species are unable to brachiate

the larger apes such as chimpanzees, orangutans, and gorillas

how has knuckle walking evolved in the ape species

each group appears to have evolved knuckle walking independently and that each has a slightly different form of locomotion.

Chimpanzees

\- Range: Largest distribution range of all modern (extant) apes

\- Shares - 98-99% DNA with chimps

\- Terrestrial Quadrupedalism: Knuckle-walking

\- Habitat: Tropical, forest savanna, montane forest

Bonobos

Also called Pygmy Chimpanzees, they can not be distinguished from common apes by size alone.

Gorillas

Largest apes, We share - 98% DNA with gorillas. Capable suspensory locomotion but large size dictates terrestrial use. Knuckle-walking

Habitat: Tropical forests, volcanic mountains.

notable skeletal structure of a primate

\- Mobile joints, Clavicles

\- Opposable Thumbs: can touch each of the four fingertips. Enables grasping

\- Hands and feet have dexterity: Arboreal adaptation

\
Especially apes and humans: Precision and power grips

Non-human primate vs human toes

Non-human primates = Abducted big toe (hallux)

Human = Adducted big toe (hallux)

Incisors

Cutting, shearing food. \*Flat, shovel-like

Canines

Pierce, tear food \*cuspid (one cusp/point), pointed

Premolars

tear and crush \*bicuspid (two cusps)

Molars

Chew, crush, grind \*four cusps

CP3 complex

Apes have enlarged canines, with an upper canine-lower premolar sectorial (cutting, honing) complex

which species have fingerprints (dermatogylphs)

all species of primates and koalas (for some reason)

what gives primates advanced vision?

\-forward-facing eyes

\- binocular vision aids in depth perception

\- Color vision in Apes, humans, OWM

Eye orbits in primates

Primates trend toward more convergent orbits while other animals tend to trend toward divergent orbits

how does primate parenting differ from other animals parenting?

Increased Parental Investment

Primates Tactile sense

Enhanced touch with dermal ridges for better gripping and sensitivity.

What are the chances of having identical finger prints to someone else?

1 in 64 million

Primate reduction of Olfaction

Primates have undergone selection for increased vision but olfactory reduction.

\- Olfactory bulb reduced

\- Occipital lobe increased

Human conchae: vs Otter and dog turbinate network

Human conchae: Comparatively less surface area. Otter and Dog turbinate network: Complex, high surface area.

Sensory trends in primates

\- Positive: selectoin for greater visual acuity

\- Negative: selection for olfaction

\- Positive: Selection for greater tactile acuity (enhanced sense of touch)

\- Hearing: generally in line with other mammals per size group

Primate Dental Formulae

Tarsiers: 2.1.3.3

Lemurs: 2.1.3.3

Lorises : 2.1.3.3

New World Monkeys: 2.1.3.2 or 2.1.3.3

Old World Monkeys: 2.1.2.3

Apes and Humans: 2.1.2.3

Homodont

Same tooth type

Heterodont

Different Types of Teeth

True: Incisors, Canines, Premolars, Molars

Toothcomb Adaptation

Canine has become an "Incisiform"

Ethnography

A scientific description of the customs of individuals and cultures

Jane Goodall

First person to immerse into chimpanzee society in Tazmania. first to discover tool use in chimpanzees and observe the "Four Year War" among them

Dian Fossey

Rwanda - Mountain Gorillas

\- Gorilla social structure

\- Practice of infanticide amongst gorillas