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Size really doesn't matter in hunter-gatherer society

Height and weight are important factors taken into consideration by both sexes when choosing a mate in post-industrial societies. But research published today suggests that size is not considered an important factor when choosing a marriage partner in more traditional societies.

Academics from the London School of Economics and Political Science (LSE) and Florida State University examined the mating practices of the Hadza ethnic group in Tanzania to determine whether size played a role in the mate choices made. Their study, published today (1 July) in the Royal Society journal Biology Letters, finds that, in contrast to post-industrial values, size really doesn't matter when choosing a mate in the Hadza forager society.

Dr Rebecca Sear|, LSE, and Professor Frank Marlowe, Florida State University, examined Hadza hunter-gatherers of Tanzania. A small group numbering about 1,000, the Hadza are a hunter-gathers who live in mobile camps averaging 30 people. Both women and men marry young: women get married at around 17-18 years with men marrying at age 20. Serial monogamy is the best way to characterise the marriage system – marriage is universal, but both men and women may divorce and remarry, and polygyny is rare (though is permitted).

The academics carried out multiple statistical tests to determine whether there was any evidence that size matters for Hadza mate choice:

  • They assessed whether married couples assorted on size (using height, weight, BMI and percent fat as indicators of size), as well as examining handgrip strength, taken as an indicator of overall strength and work capacity.
  • They asked is there a male-taller norm within Hadza marriages?
  • They assessed whether there was an association between size or strength and the total number of marriages contracted for individuals of each sex.

The results suggest that size genuinely isn't a factor when choosing a mate for this population. As Rebecca Sear explains: 'We found no evidence that the Hadza were practicing assortative mating for height, weight, BMI or percent fat for the Hadza people, in contrast to Western populations, where taller, larger men tend to marry taller, larger women.

'There is also no evidence for a male-taller norm in Hadza society. In Western populations such as the UK, social psychologists say the "cardinal rule of dating" is that the man has to be taller than the woman. This leads to the proportion of female-taller marriages in such populations being significantly lower than expected by chance – implying that height is an important factor when choosing a mate. But the number of female-taller marriages within the traditional Hadza population is no different from that expected from mating which is random with respect to height – about 9%.'

Size also didn't seem to affect the number of marriages for either sex, again unlike the industrialised populations. In the UK, for example, height seems to be an advantage for men - taller men are more likely to marry and have more marriages than shorter men – but might perhaps be a disadvantage for women. In the Hadza, neither height, nor any other size or strength variable, was correlated with the number of marriages contracted.

The examination of handgrip strength did indicate that the strength of husbands and wives was correlated. However this association was fairly weak. 'It is possible that where both men and women prefer strong partners, assortative mating comes into play, with the most attractive (strongest) man mating with the most attractive (strongest) female.' Says Dr Sear, 'but our findings indicate that as with size, strength is not considered greatly important when Hadza are choosing a mate.'

These results are significant as Dr Sear explains: "Size is usually assumed to be an indicator of health, productivity and overall quality, so this lack of size-related mating patterns might appear surprising. We may need to reassess our 'bigger is better' view of size, however, since size may not always indicate good health and productivity in all environments. Health and productivity may be signalled in alternative ways for the Hadza. An individual's health history may be more important than their size, for example, and this may be relatively well known in a small mobile population. Additionally, there may be some disadvantages to large size in food-limited societies, where costs of maintaining a large size during food shortages may be high. In post-industrialised populations, this wouldn't be a factor, and so size preferences become more of an indicator of quality.'

Ends

Contact

  • Dr Rebecca Sear, LSE, 020 7955 7348, r.sear@lse.ac.uk
  • Jess Winterstein, LSE Press Office, 020 7107 05

Notes:

How universal are human mate choices? Size doesn't matter when Hadza foragers are choosing a mate by Rebecca Sear, LSE, and Frank W Marlowe, Florida State University, was published in The Royal Society journal Biology Letters|.

1 July 2009

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