In an ironic turn of history, two of Charles Darwin’s most ardent supporters ended up disagreeing with him. The first was Robert FitzRoy, captain of the HMS Beagle and Darwin’s senior by four years, with whom Darwin had a great relationship during the sloop’s 1831-1836 round-the-world voyage of exploration. At the time, both men hewed to the conventional wisdom of the era, that God created the multitude of species on our planet, matching each to an environment suited to the particular needs of each animal. For instance, He populated a cactus-rich island in the Galapagos with finches whose long beaks were optimized for pecking bugs from the plants, while finches with short, strong beaks found themselves on another island with plentiful nuts.
More than two decades later, after Darwin realized that evolution could do everything previously ascribed to God, FitzRoy loudly castigated the biologist for his ungodliness during the great debate between “Darwin’s Bulldog” Thomas Huxley and Bishop “Soapy Sam” Wilberforce. (FitzRoy was booed into silence, according to Darwin’s friend Joseph Hooker.)
Darwin’s other great supporter Alfred Russel Wallace subsequently questioned whether evolution was a sufficient mechanism to account for all properties of all species. Wallace was the biologist whose ideas mirrored Darwin’s own thinking, and whose letter to him prompted the Linnean Society of London to have both men’s papers on evolution read at the same meeting, on July 1, 1858. In particular, Wallace found it implausible that evolution could explain abstract thought in humans, such as that required for language and morality, neither of which is necessary for survival or reproduction. Language seems to need a large brain, and Wallace wondered why humans have “a large and well-developed brain quite disproportionate to his actual requirement,” as he wrote in 1870. Brains come at a price. Aside from birthing problems, brains are heavy and fragile, and they burn energy about 10 times faster, pound for pound, than the rest of the body. Therefore, argued Wallace, our big brains must have come about through divine intervention, else evolution would have stalled at the stage of monkeys and gorillas.
Modern-day evolutionists have tackled “Wallace’s Problem,” as these concerns have collectively come to be called, the most popular response being the Social Brain Hypothesis: Early humans were essentially defensive creatures, prey for carnivores like lions and tigers, so they naturally formed into groups for defense. The number of people in a contemporary typical hunter-gatherer society is about 150, matching a proposal by anthropologist Robin Dunbar that for primates, cortex size is proportional to the size of the group. The argument goes that, to keep track of the rest of the tribe — who’s trustworthy, who’s a good provider, who’s to be avoided, who owes whom food — each individual needs a brain large enough to process and memorize this information. Not just that, but to live in harmony, she or he also needs to have some idea what all the other tribal members are thinking, that is, a unique Theory of Mind for each of scores of people.
Another recent response to Wallace’s Problem — perhaps in parallel with the Social Brain Hypothesis — is that big, intelligent, adaptive brains allowed early humans to exploit diverse environments, from arid deserts to tropical jungles to arctic tundras. This allowed them to withstand ecological disasters by moving from one domain to another.
Bottom line, Wallace considered the human brain too complex to have arisen by evolutionary selection, while Darwin trusted that evolution could explain it, even though he couldn’t muster sufficient data in his own time. Since then, especially with the advent of DNA sequencing techniques, researchers have offered many proposals in response to Wallace in addition to those I just (over-) summarized. Today, Darwinian evolution survives as, in philosopher Daniel Dennett’s words, “the single best idea anyone ever had.”
This article appears in ‘Devastation’.