Darwin, finches and the fallacy at the heart of natural parenting


Yesterday a young woman thought she would call me out on Twitter. It didn’t go quite as she had planned; she ended up looking very foolish.


In the rant that followed, McGann who apparently prides herself on her knowledge of evolution revealed that she doesn’t understand evolution. A lot of natural parenting advocates have the same problem.

The key mistake is embodied in this tweet:


Evolution teaches us that those who adapt and change are most successful, and those who insist on copying their ancestors will end up extinct.

#Breastfeeding is the result of a 7 million-year, randomized, double-blind, large-scale, longitudinal study called natural selection. This is not Appeal to Nature, but a sign post pointing right at where we should be directing the research.

So many errors in so few words:

  • evolution is not an RCT since evolution acts on all possible variables at once;
  • evolution does not create perfection;
  • evolution leads to survival of the fittest; by definition many will die.

But the key mistake, one beloved of natural parenting advocates, is the idea that we evolved for a particular environment and we should do all we can to recapitulate that environment. That’s the exact OPPOSITE of what evolutionary theory tells us. It goes back to one of Charles Darwin’s most important discoveries about the finches in the Galápagos Islands.

A few million years ago, one species of finch migrated to the rocky Galapagos from the mainland of Central or South America. From this one migrant species would come many — at least 13 species of finch evolving from the single ancestor.

This process in which one species gives rise to multiple species that exploit different niches is called adaptive radiation. The ecological niches exert the selection pressures that push the populations in various directions. On various islands, finch species have become adapted for different diets: seeds, insects, flowers, the blood of seabirds, and leaves.

The ancestral finch was a ground-dwelling, seed-eating finch. After the burst of speciation in the Galapagos, a total of 14 species would exist: three species of ground-dwelling seed-eaters; three others living on cactuses and eating seeds; one living in trees and eating seeds; and 7 species of tree-dwelling insect-eaters.


The finches can teach us critical lessons about evolution.

1. Fitness is not static.

As conditions changes, fitness changes. And conditions always change, whether it is climate, pressure from other species, local events like volcanic eruptions, etc. There is no such thing as an animal that is “perfectly fit” because there is no such thing as a static environment.

Had Darwin’s finches behaved like natural parenting advocates, they would have whined that they were adapted for ground dwelling and seed eating and therefore, they should continue living on the ground and eating seeds regardless in the dramatic change in conditions.

2. Fitness is tied to the environment.

When the ancestral finch migrated to the Galápagos Islands, its fitness was determined by the environment there. In most cases, the ancestral finch wasn’t particularly fit at all, despite its fitness on the mainland. Evolution caused the finches to evolve new traits, specific to the specific environment.

How successful do you think the seed eating finches were on islands that had very few seeds of the type they had been evolved to eat? Not very. That’s why they evolved characteristics like changes in beaks to allow them to eat different seeds and, in some cases, switched from seeds to insects.

How successful do you think the ground dwelling finches were on islands that had ground dwelling predators? Not very. That’s why they evolved to live in both cactuses and trees.

3. The most successful animals are those who can adapt, not those who remain unchanged. It doesn’t matter what happened in the past, only how well the animal can cope with present conditions.

If we anthropomorphize the finches, we can see just what is wrong with the philosophy of natural parenting.

Suppose the ancestral finches who arrived in the Galapagos had surveyed the situation on each island and announced:

“We were evolved to live on the ground and eat seeds. Therefore, we will continue living on the ground and eating seeds and pretend we are still on the mainland.

“Any finches who sample the different local seeds are benighted fools and inferior to us. They aren’t adapated to eat those seeds so they will certainly not thrive but will become obese, get cancer and auto-immune diseases and die out quickly. We will be the ones who survive.

“Any finches who choose to live in trees or, heaven forefend on ugly cactuses, are also fools and inferior to us. We were evolved to live on the ground and so we will continue to live on the ground, no matter the existence of local predators. We simply need to “trust” that the ground is safe and that will make it safe.

“Nature has rendered us perfectly evolved and all we have to do is live like we have always lived.”

They would have been wrong in every conclusion. The finches destined to be most successful were those who abandoned the way they had evolved and sought out new food sources and new places to live.

It’s not hard to see the parallels with natural parenting.

Lactivists are equivalent to finches who insisted on eating seeds because they always ate seeds. In their view, breastfeeding must be superior because humans have always breastfed. But we no longer live in the state of nature and haven’t for more than 10,000 years. The parents who will be most successful evolutionarily are those who teach their offspring to take advantage of new foods like formula when beneficial. In nature, many babies died due to insufficient breastmilk; those babies can now survive on formula. They are fitter for the current environment.

Parents who advocate co-sleeping are equivalent to finches who insisted on living on the ground even though there were new predators on the ground. In their view, co-sleeping must be superior because humans co-slept in the past. But even if that were the case, they co-slept on the bare ground in the cold. Humans haven’t slept on the bare ground in the cold since fire was mastered. Just like the finches found ground predators on new islands, we now sleep in ways that are harmful to babies: on soft surfaces, with soft bedding, some of us having smoked tobacco, or ingested alcohol or pharmaceuticals. The parents who will be most successful evolutionarily are those who let their offspring sleep in a separate bed, on a firm surface, with no bedding or soft toys.

We have no trouble understanding that finches who insisted on living like their ancestors despite a new enviroment became evolutionary failures. Similarly, natural childbirth advocates who insist that giving birth like our foremothers is “best” are destined to be evolutionary failures as their children die at homebirths or because they refused routine prenatal testing and interventions.

The ultimate irony is that evolution teaches us that those who adapt and change are most successful, and those who insist on copying their ancestors will end up extinct.