Transcript The Evolution of Entrepreneurial Spirit and the Process of

The Neolithic Revolution and the
Evolution of Life Expectancy
Oded Galor
“It is not the strongest of the species that survive, nor the
most intelligent, but the one most responsive to change”
Charles Darwin
Objectives

The origin of the rise in life expectancy since the Neolithic Revolution
Natural selection
vs. Technological advancements, income, education,…

The role of natural selection in the non-monotonic evolution of life
expectancy in the process of development

The effect of differential timing of the Neolithic Revolution across
countries and regions on the emergence of sustained differences in
life expectancy across countries and ethnic groups
The evolution of life expectancy
17,000 – 1,000 BCE
35
25
15
Mesolithic
period
Neolithic
period
Copper
age
Bronze-Iron
age
The evolution of life expectancy
in the process of urbanization (England)
43.00
41.00
39.00
37.00
35.00
33.00
31.00
29.00
27.00
1560
1600
1640
1680
1720
1760
1800
1840
1880
The evolution of life expectancy
England, 1580-2000
80
70
60
50
40
30
20
1580
1630
1680
1730
1780
1830
1880
1930
1980
Theories of Aging

The Mutation Accumulation Theory
[Medawar, 1946]
Aging is an inevitable outcome of the declining
force of natural selection in older age
Adverse mutations in the post-reproductive age have
a smaller negative effect on the survival of the genes
…Theories: Evolution of Life Expectancy

The Antagonistic Pleiotropy Theory
[Williams, 1957]
Late-activating harmful genes may be favored by
natural selection if they have a beneficial
reproductive effects in early stages of life.
(Pleiotropy - multiple effects of a single gene)
…Theories: Evolution of Life Expectancy

The Disposable Soma Theory
[Kirkwood and Holliday, 1979]
Optimal allocation of metabolic resources between
reproduction and maintenance.
The Disposable Soma Theory
Evolutionary trade-off between:
Resources channeled toward:

current reproduction
&

somatic investment 
longevity & future reproduction
…The Disposable Soma Theory
Evidence:

Longevity is correlated with resources devoted to cellular
repair and maintenance

Capacity of somatic cells to carry out effective maintenance
and repairs (e.g., DNA repairs, accurate gene regulation,
tumor suppression, and antioxidants), governs the time taken
for damage to accumulate
[Kirkwood (1998), Williams and Day (2003)]
Main Hypotheses

The Neolithic Revolution increased the
extrinsic mortality risk
- rise in population density
- domestication of animals
- increase work effort
- poorer nutrition (e.g., reduced meat intake,
reduced mineral absorption by the cereal-based diet)
Time Trend in Pre-Columbian Health
100
90
80
Health Index
70
60
50
40
30
20
10
0
-6000
-4000
-2000
BC
0
2000
AD
Date
Source: Richard H. Steckel
Health Index

Skeletal infections - inflammatory responses to bacterial invasion

Iron deficiency anemia - nutritional deprivation, low body weight,
chronic diarrhea, parasite infections

Dental health -- indicator both of oral and general health

Degenerative joint disease -- mechanical wear and tear on the
joints of the skeleton due to physical activity

Enamel hypoplasias - enamel deficiency commonly found in the
teeth of people whose early childhood was biologically stressful

Trauma
…Main Hypothesis

This deterioration in the health environment increased the
evolutionary optimal allocation of resources towards somatic
investment, repairs, and maintenance
(e.g., enhanced immune system, DNA repairs, accurate gene regulation, tumor
suppression, and antioxidants)
Short-run: (the composition of the population is unchanged)
Life expectancy declined
Long-run: (an evolutionary process)
Evolutionary advantage to individuals who were genetically
pre-disposed towards higher somatic investment
 Increased representation of individuals who are
genetically pre-disposed towards higher somatic investment
 Life Expectancy increases
…Main Hypotheses

The deterioration in the health
environment:
 triggered
the observed improvement in
life expectancy since the Agricultural
Revolution
 was
a necessary condition for the dramatic
recent improvement in life expectancy
…Main Hypotheses

Differences in the timing of the Neolithic
Revolution across regions led to sustained
differences in life expectancy across
countries.
…Main Hypothesis
The rise in the extrinsic mortality risk
enhanced the genetic potential for longer life
expectancy (i.e., life expectancy in a riskfree environment)
enabled the dramatic impact of recent
improvements in health infrastructure on the
prolongation of life
Rapid Evolutionary Changes in Humans in
the past 10,000 years

Lactose Tolerance


Gluten Tolerance


Variations in the ability to tolerate lactose across regions is inversely
related to the differences in timing of the transition to agriculture across
regions and thus in the domestication of dairy animals in the Neolithic
revolution
Variations in the ability to tolerate a protein present in wheat, rye,
barley, and some oats, first domesticated in the course of the
agricultural revolution, is inversely related to the distance from the
Fertile Crescent
Genetic immunity to malaria - Sickle Cell Trait

Variations in natural immunity to malaria is related to the engagement
in slash-and-burn agriculture
…Rapid Evolutionary Changes in Humans in
the past 10,000 years

700 regions of the human genome have been
reshaped by natural selection within the past
5,000 to 15,000 years
Voight et al. (2006)

ASPM (a specific regulator of brain size in the
lineage leading to Homo sapiens) arose in
humans merely about 5800 years ago and has
since swept to high frequency under strong
positive selection
Mekel-Bobrov et. al (2005)
Testable prediction

Populations that experienced the
Neolithic Revolution earlier have
higher life expectancy
Fig.1 - Life Expectancy and Timing Since Neolithic
JPN
HKG
CHE
SWE
ITA
AUS
ESP
CAN
FRA
NZLLUX NLD
NOR
CYP
MLTARESGP
GRC
DEUAUT
CRIISR
BEL CHL
GBR
FIN
USA
DNK
KWT
PRT
IRL
CUB
SVN
KOR
CZE
URY
PAN MEX
BHR
ARG
POL
HRV
BIH
LKALBY
OMNQAT
ECU
ALB
VEN
MKD
MYS SVK
YUG
SYR
BLZ LTU TUN
BGR
COL
SAU
LBN
HUN AZE
JAM
EST
ARM
JOR
TTO
LVA SLVPRYBRA
GEO
DZA
CHNIRN
THA
PER
VNM
NIC
MAR BLRPHL
SUR
EGY
KGZ
TUR
UZB MDA
HND DOM UKR
GTM
IDN
KAZ
RUS
TJK
BOLMNG
TKM IND PAK
GUY
BGD
BTN
NPL
MMR
YEM
80
70
60
GABGHA
SDN
KHM
SEN
GMB
TGO
PNG
BEN
GIN
NAM
MRT
COG
HTI
KEN
ZAF
MLI
CMR
TZABFA
CIV
SWZ
SOM
UGA
GNB
TCD
NGA
NER BDI
BWA
MOZ
LBR ETH
LSO
RWA
AGO
MWI SLECAF
ZWE
ZMB
MDG
50
40
2
LAO
4
6
8
Weighted Timing Since Neolithic
10
Fig.2 - Life Expectancy and Timing Since Neolithic
Covariates Adjusted
20
TUN
DZA
EGY
GHA
10
LKA
0
FIN
-10
TGO
SDNCRI
GMB
SEN
ECU BEN
BGR
NIC
SYR GRC
NZL
PAN
PHL CHL
CHN
HND
PRY
COL AUS ESP ITA
SLV
POL
MLI
URY
MEX
PRT
JOR
SWE
FRAIRN
MYS
KEN
CAN
IDN JPN
CHE
VEN
PER
KORNPLTHABEL
COG
HUN
GTM
DEU AUTDOM
NLD
GBR
ISR
UGAARG
NER
NOR
IND
BGDMOZ
IRL BRA
LBR
PAK
KWT
USA
SLE
TTO
BOL MWICMR
DNK
TUR
GUY
RWA
CAF
PNG
LSO
SWZ
ZMBZAF
ZWE
HTI
BWA
-20
-4
-2
0
2
Weighted Timing Since Neolithic
4
Evidence (other species):

The effect of a rise in extrinsic mortality
risk on life expectancy is ambiguous
[Williams and Day (2003)]

Recent study: Guppies that were
exposed to higher extrinsic mortality risk
had a higher life expectancy in a riskfree environment (i.e., lower intrinsic
mortality rate) [Reznick et al. (Science, 2004)]