Occam's Razor is a widely valued principle in science and beyond. But as the exceeding complexity of our world becomes increasingly apparent, is it time to give up on the virtue of simplicity when it comes to understanding the universe, asks Angela Potochnik.

Simple explanations are widely valued. Occam’s Razor, named for a medieval philosopher, urges us to adopt the simplest theory the evidence allows. Customarily, this is understood as the idea that simple theories are more likely to be true. This idea has been widely influential, and perhaps especially so in science. 

But here’s the problem. It’s increasingly clear that the world we inhabit is exceedingly complicated. Germs cause disease, but it turns out that exposure to germs isn’t the only relevant factor to whether you get sick, and so-called “lifestyle diseases” such as heart disease and strokes aren’t caused by germs at all. 

In 2003 the Human Genome Project completed a full account of human genes, but it has been hitting home since then that human genes are tremendously variable and the influence of individual genes frustratingly difficult to identify. The former observation spurred the 1000 Genome Project, while the latter is such a serious problem it has been named: missing heritability. Scientists now also appreciate that humans are significantly influenced by the genes of the bacteria we host, which outnumber our own cells. Getting to the bottom of this influence is the aim of the Human Microbiome Project. Your health is also influenced by your mother’s and grandmother’s lived experiences, including their stress levels: this is one element of what’s called epigenetics.