1. Humans are apes that evolved from early hominins like Australopithecus. While we share many traits with other apes, factors like increased brain size, imagination, language, tool use and cooperation made humans unique. 2. Several genetic changes were important in human evolution, including genes related to jaw size, language processing and tool-making abilities. Traits like bipedalism, hunting and cooking meat also contributed to increasing brain size. 3. Many human behaviors and traits have evolutionary explanations as adaptations, such as attractiveness preferences, jealousy, step-parent cruelty, and homosexuality. Humans continue evolving genetically and culturally, as seen with diet adaptations and changing beauty standards.

1. The story of the naked apes:
what makes us unique?
By
Ranajit Das
Manipal Centre for Natural Sciences (MCNS)
Manipal University

2. Today’s talk
• Humans are apes: the journey of hominins
• What makes humans unique?
• Traits from the past
• Are we still evolving?

3. We, the naked apes…
Humans are primates
1. Grasping hands—precision
grip and power grip
2. Binocular and color vision
with overlapping fields of
view
3. Large brain—allows fairly
complex social systems
4. Nails instead of claws

4. Where do we belong?

5. Gross level changes: fusion origin of chromosome 2
We have one less chromosome than
our close relatives

6. Published by AAAS
A. Gibbons Science 326, 36-40 (2009)
The Human ‘family’

7. Published by AAAS
A. Gibbons Science 326, 36-40 (2009)
Ardipithecus ramidus
Existed 4.3 Mya

8. Then there were two early lineages of
hominins
Australopithecines

9. ‘Gracile Australopithecines’: Australopithecus afarensis
“Lucy”
Our direct ancestors existed ~3.0 – 3.9 Mya

10. • Big and strong in
size
• Existed ~1-2 Mya
• A “side branch” of
the hominin tree.
- Left no living
descendents.
‘Robust Australopithecines’: Paranthropus robustus

11. The genus “Homo”
Our story begins here…

12. Homo erectus
(ergaster)
—1.8 Mya to 500,000 ya.
• Face of modern
human
• More socially
advanced
• Sophisticated stone
tools aided in hunting
• Used fire
• Migrated out of Africa
as far east as
Indonesia.

13. Homo neanderthalensis
– Existed 300,000 -
30,000 years ago
– Similar to modern
humans—muscular,
fully erect,
dexterous, large
brains. Body type
adapted to cold
weather.
– Developed ritualistic
burial ceremonies

14. Anatomically Modern Human (AMH):
Homo sapiens
– We stared our journey
200,000 years ago
– Had the power of imagination
– Artistic and made precision
tools

15. Human migration routes

16. Aboriginals Down under are of Indian
ancestry?
A wave of settlers from India to
Australia 141 generations ago
Aborignals were found to have
up to 11 per cent of their DNA
from Indian descent

17. Trends in Human Evolution
• Increase in brain size
• Upright bipedal walking
• Weaker jaw muscles
• Eye brow bones becomes
smaller
• Flattening of cheekbone
• Decrease in protrusion of jaw
bone
• Decrease in sexual
dimorphism
H. sapiens vs. A.
afarensis
pelvic bones.

18. One summary of hominin fossils

19. We are all the same: The differences
are all external

20. WHAT MAKES US UNIQUE?
No human ‘family’ member survived the ice age.
Even the Neanderthals, who survived through this
harsh period got extinct soon. Only a small group of
anatomically modern humans, going through a
population bottle neck, successfully survived the ice
age and flourished…

21. 1. Imagination and creativity: the
power of abstract thinking

22. Imagination is an outcome of high brain
volume

23. • For most
tissues humans
have very little
genetic
divergence
from chimp
• However, in
brain, humans
have diverged
considerably
more

24. Increased meat eating helped our
brain to grow
Humans are the only obligatory meat-eating ape

25. 2. Language
Hyoid bones of Humans (left) and Chimpanzees (right)
Hyoid bone supports the tongue
and help putting the sounds
together into a clear structure that
everyone could understand – we
call it ‘language’

26. Processing language in the brain
• Complicated process
• Involves many brain
areas
• Broca’s and
Wernicke’s areas at
the surface of the
brain major players

27. FOXP2 aids in language processing
in brain
People with mutations in FOXP2 show
language processing defects
Mutations in FOXP2 cause “developmental verbal dyspraxia (DVD)”

28. Unique mutations in FOXP2 helps
us process language
Neanderthals could also process language

29. 3. Loss in size of the jaw muscles
• Stronger jaw muscle
require sagittal crest
• But presence of
sagittal crest hinder
cranium expansion
• A loss in size of the
jaw muscle allowed
the cranium to
expand, helping to
increase brain size
Robust Australopithecine Gracile Australopithecine

30. Strong jaw muscle is associated with
MYH16 gene
• Humans have an inactive MYH16 (pseudogene)
• There is a 2bp deletion in exon 18 only in humans
• Loss of MYH16 in jaw muscles affects the size of
the muscle

31. MYH16 got
inactivated
during the
advent of our
journey…

32. 4. Intricate tool making ability: opposable
thumb

33. Our technological innovation was the
key for our successful migration out
of Africa

34. HACNS1, an enhancer, aids in advanced
tool making
• Plays an important role in
human specific changes
to hands and feet
• An important candidate
for contributions to
human bipedalism and
tool making

35. 5. Extremely cooperative animal
• While both chimps and humans cooperate,
humans always help more
• Children are innate helpers. Humans act
selflessly till social norms set in
• The sense of fairness begins is inborn
“(Unlike humans) chimps will only cooperate if there is something in it for them” -
Michael Tomasello (Max Planck institute for Evolutionary Anthropology, Leipzig,
Germany)

36. The cooperative behaviour evolved
from group hunting
• Associated with the increase in the volume of our brain
• Our brains needed more fuel
• Collaborative hunting played a key role in gathering
more food

37. 6. Emotional lacrimation (Crying)
• Evolved alongside cooperative behaviour
• Enhance emotional communication within social
groups
• Increased affective communication
• Used to elicit mercy from an antagonistic enemy

38. 7. Prolonged labor
• Earlier onset and longer
duration of labor
• Humans have a large
braincase in proportion
to the birth canal
• Prolonged labor
protects child/mother
from damage due to
increased head
circumference

39. We are just the relics of the past -
Everything we do have some
evolutionary connection
“Humans and animals only differ in
degree, not kind” – Charles Darwin

40. 1. Attractiveness: Beauty is actually
not in the eyes of the beholder
• Have two components:
Fitness and Relatedness
• Females prefer facial
symmetry in men: an
indication of health and
fitness
- very similar to
other mammals (Deer and
antelopes: antler
symmetry)Both photos are of the same man:
Which one do you like?

41. Males across all cultures prefer the same shaped females
as most attractive: specific hip to waist ratio
Picking the most fit mates by sight?

42. Females can detect genetic
relatedness by smell?
• Help to avoid inbreeding
• Smell associated with the genotype of that individual
• MHC (HLA-A) in action
• Famous sweat shirt experiment

43. 2. Jealousy
• An adaptive feature: a
naturally selected trait
• Evolved from resource
protection
- Resource can be
food, mate or anything
else that can improve
one’s quality of life
The Cruel Sister, by John Faed (1851)

44. 3. The ‘cruel’ step parents
• Strong selection towards investing resources in
genetic offspring: Direct fitness
• Humans invest more time in genetic offspring

45. Stressful life of step-children
• Step children are seek more often and have lower
reproductive success
• Result of a stressful environment
• Cortisol (stress hormone) in action

46. Cruelty towards step children is an
evolved version of infanticide
Note to the age of most infanticide incidents: it matches other mammals in
which infanticide is common

47. 4. Certain things we’re born to fear
• Fear of spiders associated
with early human life in
Africa
• Fear of reptiles stretches
back to early mammals who
had to survive in an
environment dominated by
deadly reptiles
• Fear of darkness associated
with cavemen wanting to
escape predators at night

48. 5. Smile evolved from fear
• Smile evolved from display of teeth
when afraid as a defense mechanism
• Similar to facial expressions of other
primates: same muscles involved
• The fear expressions: bared teeth,
flattened ears, and taut neck, happens
when an animal is trapped or
threatened but can't escape
• Sign of submission to the dominant
member of the group in Rhesus:
escape fight

49. 6. Homosexuality: not an uniquely
human trait
• Observed in >400 animal species
• Pre-wired: genetic
• Genderblind (gb) mutant male
Drosophila show strong homosexual
courtship
• Very common in bonobos
• May be associated with X
chromosome

50. 7. We still harass the weak
• Same sex harassment
evolved from pecking
order found in many
mammals
• Opposite sex harassment
(male to female) evolved
from sexual coercion
seen in primates

51. Are we still evolving?
“You can't even begin to understand biology, you
can't understand life, unless you understand
what it's all there for, how it arose - and that
means evolution”.
- Richard Dawkins

52. • Copy number variation in AMY1 gene: High starch
diet people have more AMY1 copies (14 copies in
Japanese people compared to ~6 for Africans)
• We are gradually losing our wisdom tooth
• Blue eye colour: Evolved after last Ice Age

53. All modern South Asians are admixed
but genetically distinct
-0.03 -0.02 -0.01 0.00 0.01 0.02
-0.03-0.02-0.010.000.010.02
a$V3
a$V2
PCA2
PCA1

54. Recent genetic differences between North
and South Indians
• Mutations in
SLC24A5 associated
with skin
pigmentation:
influence skin colour
variation
XP-EHHscore
Chromosomal position
• Long stretch of Chr1 has
undergone recent
Selective sweep among
Gujarati people
compared to Telugu
people

55. Even the concept of ‘beauty’ is evolving
Selection on body-mass index
changed over last 100 years: smaller
and chubbier (higher body-mass
index) women had the initial fitness
advantage but the trend reversed in
favour of those taller and thinner
(Milot and Pelletier 2013)
Hannah
Primrose,
Countess of
Rosebery
1851-1890
Marilyn Monroe
ca. 1955
Kate Moss
ca. 1995

56. ‘Beauty’ in modern world
Among females ‘oval’ and ‘heart’ face
types are most preferred
Among males ‘rectangular’ face
type is most preferred
Assessing human mate preference dilemma from a multifactorial
point of view
An anonymous survey pertaining to this project can be found here: https://www.surveymonkey.com/r/TGMP858

57. “An American monkey, after getting drunk on
brandy, would never touch it again, and thus is
much wiser than most men.”
― Charles Darwin
We pretend to be smart and intelligent but the
reality is something else…