Legacies of Human
Evolutionary
History: Effects on the Individual
Question:
Does the flexibility of human behavior pose
problems for the species?
Evolved Biology and
Contemporary Lifestyles—Is
there a Mismatch?
Some aspects of modern human lives are
disconnected from our evolved biology
In past 10,000 years, pace of cultural
change has accelerated, changing the
context of human evolution
Changing Contexts
Biocultural Evolution and the Life
Course
Biological development occurs from embryo
to old age
Cultural factors interact with genetically
based characteristics
Human Growth and Development
Today and in the Past
Human growth continues through late teens or
early 20s
Three major spurts are typical, including first
two trimesters in utero, first four years and
the adolescent growth spurt
Adolescent Growth Spurt
Pronounced increase in growth rate at
puberty, compared to fairly steady level
maintained since about four years
Western teenagers typically grow around 4
inches per year
Followed by decline in rate of growth until
adult stature is achieved by late teens
Human Brain Growth
25% of its adult size at birth
50% at six months
75% at 2.5 years
90% at 2 years
95% at 10 years
Human Brain Growth
Such a small amount of growth before birth is
unusual for primates and mammals
Selective advantages of such an
underdeveloped brain
Exit through narrow pelvis modified for
bipedalism
Brain develops in stimulating, cultural
context
Nutritional Requirements for
Growth

Nutrients needed for growth, development, and body
maintenance include: proteins, carbohydrates, fats, vitamins
and minerals.

The amount we need of these nutrients coevolved with foods
available to humans throughout evolutionary history.

Deficiencies during pregnancy can last a new child’s lifetime

The specific pattern of amino acids required in human
nutrition (essential amino acids) reflects an ancestral diet
high in animal protein.
Essential Amino Acids
The 9 (of 22) amino acids that must be
obtained from the food we eat because they
are not synthesized in the body in sufficient
amounts.
Comparison of Diet (Table 131)
Total dietary
energy (%)
Preagricultural
Diet
Contemporary
Diet
Recently
Recommended
Protein
33
12
12
Carbohydrate
46
46
58
Fat
21
42
30
Alcohol
~0
(7–10)
—
Cholesterol (mg)
520
300–500
300
Comparison of Diet
Total dietary
energy (%)
Preagricultural
Diet
Contemporary
Diet
Recently
Recommended
Fiber (g)
100–150
19.7
30–60
Sodium (mg)
690
2,300–6,900
1,000–3,300
Calcium (mg)
1,500–2,000
740
800–1,500
Ascorbic acid
(mg)
440
90
60
Preagricultural Diet

Prior to 10,000 years ago

Typically high in animal protein, low in fats, particularly
saturated fats

High in complex carbohydrates (including fiber), low in salt,
and high in calcium

Human health declined in most parts of the world,
beginning about 10,000 years ago

“Epidemological transition” marked by rise of malnutrition,
drop in life expectancy
Once adaptive, now
maladaptive

Ability to store fat, an advantage when food availability
often alternated between abundance and scarcity

“Feast or famine” biology incompatible with context of
constant feast

80% of new cases of type 2 diabetes appearing
between now and 2025 will be in developing nations

Type 2 diabetes, linked to poor diet and inadequate
exercise, occurring in children as young as 4

“Epidemiologoical collision” in countries where
malnutrition and infectious diseases collide with obesity
Other Factors Influencing Growth
and Development: Genes and
Environment

Genetics – set the underlying limitations and potentials for
growth and development

Environmental factors can influence growth and
development, but an individual can not exceed their
genetic potential.

Epigenome-Instructions that determine how genes are
expressed in a cell

Epigenetics-Changes in phenotype that are not related to
changes in underlying DNA and that may result from the
interaction between the genotype and the environment
Other Factors Influencing Growth
and Development: Genes and
Environment
Hormones – produced by endocrine glands
Growth hormone has an impact on almost every
cell in the body.
Cortisol, elevated during stress, suppresses
normal immune function during high levels
Endocrine Glands
Glands responsible for secretion of hormones
into the bloodstream, i.e. pituitary, thyroid, and
adrenal glands, ovaries and testes
Variation in Growth Hormones
The Human Life Cycle
1.
Prenatal begins with conception and ends with birth.
2.
Infancy is period of nursing.
3.
Childhood, or juvenile phase, is period from weaning
to sexual maturity (puberty in humans.)
4.
Adolescence is from puberty to the end of growth.
5.
Adulthood is the completion of growth.
6.
Menopause beginning one full year after the last
menstrual cycle
Life History Theory
Typical developmental patterns shaped by natural
selection
Entire life course thought of as a series of tradeoffs among various life history traits
Life Cycle Stages
for Various Animal Species
Pregnancy, Birth and Infancy
Cultural and social factor shape infant’s
development in utero
Birth is dangerous event and often surrounded by
ritual significance
“Underdeveloped” human infant brains adapted to
developing in cultural environments
Diameter of Birth Canal and
Head Length and Breadth of
Newborns
Nursing
Most anthropologists suggest three to four years of
nursing was the norm for humans in our evolutionary
past
Agriculture produced more options for supplemental
foods and could quicken weaning
Nursing can act as birth control
Childhood
Humans have unusually long childhoods, which
illustrates importance of learning for human
adaptation
Humans might be unique in practice of
provisioning for juveniles
Providing for Juveniles
Lion
Baboon
Macaque
Chimpanzee
Human Populations
!Kung
Yanomamo
Paleoindian
Percent Who Survive
Weaning
Adolescence
28
15
45
33
42
13
48
38
80
73
86
58
50
50
Adolescence
Rapid growth seen during adolescent growth
spurt unique among primates
Adulthood
Women in our evolutionary past likely
experienced fewer menstrual cycles
throughout life
Most were more often pregnant or nursing
Menopause
Advantages
“programmed” to live 12 to 15 years beyond
birth of last child since human parenting involves
years of post-partum care
Grandmother hypothesis
Women freed to provide high-quality care to
grandchildren
The Trend in Age at Menarche in
Europe
Aging and Longevity
Attitude towards old age is culturally determined
Top 5 causes of death in the US are heart disease,
cancer, stroke, accidents, and chronic obstructive
lung disease (no longer in this order)
Senescence, the process of physiological decline in
all systems of the body occurring toward the end of
the life course
The decline is gradual throughout adulthood
Life Spans (Table 13-4)
Organism
Bristlecone pine
Tortoise
Human
Blue whale
Indian elephant
Gorilla
Domestic dog
Rabbit
Rat
Approximate Maximum
Life Span (in years)
5,000
170
120
80
70
39
34
13
5
Pleiotropic Genes
Genes that have more than one effect.
Genes that have different effects at different
times in the life cycle.
May help to explain evolutionary reasons for
aging, but do not explain the causes of
senescence
Mitochondrial Theory
Free radicals produced by mitochondria
diminish efficiency of cellular energy
production
Ultimately leads to organ failure
Teleomere Hypothesis
Repeated sequences of
DNA at end of
chromosomes
Get shorter as
organisms age
Ultimately, impairs
healthy cell division
Changes in Life Expectancy
Due to AIDS in Seven African
Nations
Effects of Technology on the
Brain
Our brains coevolved with technology and
language development
Contemporary technological change may be
much more rapid than evolution can keep up
with
But, brains may be developmentally modified
by using new technologies
Are We Still Evolving?
Socioeconomic and political concerns have
powerful effect on our species today
Anthropologists can not predict whether
humans will eventually become a different
species or become extinct
There is little doubt that the human species will
continue to evolve or become extinct
Why It Matters
The “small but healthy hypothesis” states that
small adult stature under circumstances of low
resource availability is adaptive in that small
adults would need fewer resources and would
fare better under chronically stressful
conditions.
Why It Matters

Anthropological and evolutionary perspectives
reveal that small body size also means small organs,
less ability to perform work, and lower reproductive
success.

Even if a baby whose mother was malnourished
during pregnancy is well nourished from birth on, the
child’s growth, health, and, for females, future
pregnancies appear to be compromised.

This has clear implications for public health efforts
that attempt to provide adequate nutritional
support to pregnant women.