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Razib has responded to my disagreement with his statement that any given hunter-gatherer infant is far more likely to reach reproductive age than any given offspring of peasants. And he’s confident with his standing. I’ve done some reviewing of the literature and I still think that the probability that a child of an agriculturalist will reach reproductive maturity is higher than that of a hunter gatherer. Hell, that’s why there’s been a population boom ever since the Neolithic revolution. Anyways, in my previous post I outlined some of the ethnographic reasons why I think so. In this post, I’ll share some of the demographic data that supports my hypothesis.

On page 198 of the text, Hunter-Gatherers: An Interdisciplinary Perspective average parity rate for healthy hunter-gather women, Renee Pennington explains that the average fertility rate for a hunter-gather woman is 6-8 births during her lifetime. The expected child-bearing age of hunter-gatherer women ranges between 24 and 37 years. The data comes from surveys of hunter-gatherers in the early 1990’s.

I averaged out the 2008 total fertility rate (TFR) of all countries provided by the CIA. I couldn’t find TFRs for strictly agricultural populations so I will assume that most, if not all the countries, are agricultural given that  very few large hunter-gather populations exist. The average fertility rate is around 1-4 births during a modern day agriculturalist woman’s life time. The factbook mentions that the child-bearing age for women surveyed is between 15-49 years old.

Given this, I think we can see that hunter-gatherer women birth more frequently within a more restricted time frame. Part of this is due to affects of a hunter-gatherer lifestyle. But one of the flaws with my assumption that modern TFRs provided by the CIA come from agriculturalists can be seen already, because we know that agriculturalists have on average more children than hunter gatherers. Razib mentioned Fischer’s review of birth rates in colonial New England was upward to 10, and I’m not surprised.

Because of this discrepancy, we need to factor in the survivability of the newborn. Razib mentions that there’s a “greater likelihood of dying early among farmers because there were just more of them floating around,” so to compare, I researched the infant mortality rate (IMR) which is defined as frequency of deaths in the first year of life per 1,000 live births. These two tables describes the IMR in modern day hunter gatherers vs the IMR in modern day agriculturalists.

Table 1: IMRs Among Hunter-Gatherers

IMR (per 1000 births)
Savanna Pumé (2007) 34.6%
Hadza 21.0%
Aeta 37.0%
Asmat 34.0%
Average 31.7%
Standard Deviation 7.22%

Table 2: IMRs Among Agriculturalists

IMR (per 1000 births)
River Pumé (2007) 13.0%
Rural England and Wales (1900-1904) 13.1%
Gulbarga District of India (2008) 6.70%
Afghanistan 15.7%
Sri Lanka 1.95%
Angola 18.4%
Average 11.8%
Standard Deviation 6.10%

My hunter-gatherer data comes from Kramer & Greaves, “Changing Patterns of Infant Mortality and Maternal Fertility among Pumé Foragers and Horticulturalists.” My agriculturalist data has come from differing sources, some from the most recent CIA World factbook, and others from newspapers, research papers, which I’ve linked up. Significant differences emerge when we look at the infant mortality experiences between these two sustenance strategies, almost three times greater infant moralities among hunter-gatherers than their farming counter parts.

Average IMRs of Agriculturalists versus Hunter-Gatherers

Average IMRs of Hunter-Gatherers versus Agriculturalists

Now you could argue that higher IMRs could be due to the lack of exposure hunter-gatherers have to pathogens and health care on average compared to sedentary agriculturalists. That’s precisely why I put the Pumé example in there. The Pumé are a linguistic group of people who live on the border of Venezuela and Columbia. Populations that live in savanna ecosystems are the hunter-gatherers, where river dwelling populations are the farmers. Both populations have similar vaccination patterns, and yet the hunter-gathering population experiences more infant moralities than the farming population.

Why?

Newborns are particularly susceptible to shortfalls in caloric intake. They are dependent on their mother’s milk for calories. I know the agricultural diet is nutritionally deficient, I’m not gonna argue that it is. The farmers’ diet has made us less robust and susceptible to dietary diseases. But it is rich in calories and the greater accessibility to calories that come with agriculture improves likelihood of young children reaching sexual maturity.

The hunter-gatherer diet fluctuates caloric intake based upon the availability of food sources and cultural taboos, and that has deep impacts on their survivability. You can see from the data that I presented that 1/3 of all hunter-gatherer newborns will die before 1 year. I didn’t extend later life mortality rates, but to summarize, those that do survive half live to see the age of 15. So for every 8 births, a hunter-gatherer woman gives, only 6 or so are expected to live to childhood. Of those 6, only 3 see adolescence. And of the 3 teenagers, only 1 is expected to reach 50 years old.

Razib equates hunter-gatherers to lions, and farmers to antelopes. Lion cub mortality rates are higher than antelopes, upwards of 80% of cubs do not make it to adulthood. Whereas antelope calves, if they survive predation, have much more greater chances at seeing sexual maturity. It is much more precarious to count on mom to provide milk and hunt at the same time, than it is to graze. So, this issue is less about absolute availability and more about reducing the periodicity and amplitude of nutritional stress. And this is one of the reasons why the agricultural diet has ‘won’ over many humans, even despite the many shortcomings it has.

    KAREN L. KRAMER, RUSSELL D. GREAVES (2007). Changing Patterns of Infant Mortality and Maternal Fertility among Pumé Foragers and Horticulturalists American Anthropologist, 109 (4), 713-726 DOI: 10.1525/AA.2007.109.4.713
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