14 May 2020

The nature v nurture debate: A 'scientific zombie'

From Afternoons with Jesse Mulligan, 1:15 pm on 14 May 2020

A paper has been published in the hope it will thrust a multi-disciplinary stake through the heart of the “nature versus nurture” debate once and for all.


University of Otago's Department of Zoology’s Professor Hamish Spencer and Professor Marlene Zuk, of the University of Minnesota, have likened the either-or notion to a “scientific zombie”, parading through corridors of learning after having already died decades ago.

The authors say the persistence of the false dichotomy has helped distort the public's view of science and continues to fuel fruitless, uninformed debates.

Their views were published this week in BioScience. They argue the idea that either your genes (nature) or your environment (nurture) dictate the outcomes in your life leads to flawed conclusions on matters such as intelligence, sexual orientation and bad behaviour.

No trait is caused by either genes or the environment or even by a combination of the two. Interaction between the two factors is the important feature. The paper also argues that genes do not and cannot code for behaviour or any other characteristic.

“It’s not one thing or the other,” Professor Spencer told Jessie Mulligan.

“The argument that we’re making is that, well it’s both, but it’s not just both that the effect of one depends on the other. So, the effect of your genes depends on which environment you’re in and the effect on your environment depends on what genes you have.

“Geneticists, environmental biologists, most biologists in fact, have known that genes and environment interact for decades.

“But for some reason we don’t seem to get past the dichotomy of ‘is it nature or nurture’ and that’s why we call it a ‘zombie’ idea, because it’s an idea we know is wrong and should be dead, but it isn’t actually dead.”

Removing the ‘nature versus nurture’ lexicon from scientific discourse makes it easier to understand the field and transcend false assumptions so that the importance of interaction is fully appreciated.

“We do want to know why individuals come to be the way they are and the dichotomy we have of nature or nurture is not very productive because we know it’s wrong,” Spencer says.

“We’d much rather have positive views. Just to give you an example. We already know people have a gene that predisposes them to breast cancer – that predisposition tells you about interactions.”

Spencer uses the example of genetics making some people are susceptible to certain diseases, pointing out that how that person interacts with their environment will ultimately determine whether they develop illness.

“The gene that predisposes women to breast cancer and ovarian cancer doesn’t mean you will get cancer. It’s not written in their genes they will get cancer, it just predisposes them.

“And, indeed, if they change their environment - and one of things they can do is take an oral contraceptive - they lowers the risk of ovarian cancer.

"So, we have to understand that the effect of your genes depends on your environment and in this case, that’s whether a woman takes a contraceptive and the effect of the contraceptive pill depends on the gene, so whether you get cancer is going to be effected by both. What’s really interesting is the interaction.”

He says the paper was written as a means of focusing people’s minds on the need to avoid keeping the ‘zombie’ alive and to protect scientific endeavours from falling victim to its deadening effect on rational debate.

“There’s a bit of statistics, a bit of philosophy, zoology and human biology in there… We talk about the zombie idea. I have to give Marlene credit, that’s one of her phrases.

"Marlene is a great scientist but also a great populariser of science and she was thinking about this very idea and we’d been talking about it for a while. She said it would be good to write a short paper aimed at biologists just to remind them of what they already know, but also to put it in a language that really appeals.”

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