Readers Respond to "Still Evolving (After All These Years)"

QUESTIONS OF LOGICspecial issue on evolution, a question based on a false premise is asked: What makes human special? As a minor branch on a vast evolutionary bush, modern humans have been roaming the earth for no more than a few hundreds of thousands of years—too little time to demonstrate if the evolution of large brains is a successful strategy for long-term survival of the species. If any life-form were special, it would be bacteria, which will be here long after the human experiment is a distant memory.

JEFF SCHWEITZER

I find myself likening the attempt to pinpoint where humanity began to preschoolers theorizing about candy they've found scattered about a picnic area. A Hershey bar in the grass suggests chocolate grows there, whereas a Butterfinger by the table surely fell out of a pocket.

Inventing scenarios to try and fit observations are where theories come from. Still, beware that in our eagerness to explain, we risk elevating accidents of the discovery process to primary evidence.

DAVID K. ELLIOTT

MODERN EVOLUTION“Still Evolving (After All These Years),” human populations continue to evolve today. But Hawks does not discuss the possible consequences of some of the evolutionary pressures that have been altered in the past century by medicine and public health. Could modern medical intervention inadvertently result in the survival and spread of genetic mutations that would otherwise have been eliminated or in the loss of protective genes?

MARTIN J. GREENWOOD

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CURIOUS CREATURE“If I Had a Hammer,” Ian Tattersall cites our capacity for symbolic reasoning as one of the traits unique to humans that led to the rise of our species' dominant position on the earth. I believe that our highly developed curiosity is another key, uniquely human trait. Without motivation, our capacity for symbolic reasoning would be of little use, and curiosity could have provided it.

LEON M. ROSENSON

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CONTRADICTORY VIEWS?

In his article, Tattersall writes that “a population needs to be small if it is to incorporate any substantial innovation, genetic or cultural. Large, dense populations simply have too much genetic inertia to be nudged consistently in any direction.” But in his article, Hawks asserts that “the huge and rapidly increasing population size of our ancestors gave them many more rolls of the dice. As human populations have spread into new parts of the world and grown larger, they have rapidly adapted to their new homes precisely because those populations were so big.”

MEL TREMPER

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SEX AND THE EXPERIMENT[“Vive la Différence,” Forum], R. Douglas Fields claims that doing so would create problems because it would increase data variability. That is balderdash.

First, differences between male and female participants can be captured by many different statistical treatments, which allows researchers to compare groups without increasing error variability.

Second, the idea that reduced variability is the aim of all scientists is scary. I could reduce data variability on chairs by only studying purple ones that were 0.5 meter high. Then I could make only generalizations about those particular chairs.

CYNTHIA WHISSELL

Fields incorrectly states that when sex is added to an experiment, it cuts the sample size in half and increases variation. In research or experimental design, one reduces variance by eliminating differences within the sample or by building differences into the design. Thus, at the postassessment phase, one might have a “two-by-two design” (experimental group versus control group and male versus female).

DAVID LOPEZ-LEE

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