Junk DNA is gradually making its way into mainstream textbooks

The idea that most of the human genome is junk originated more that 50 years ago. Since then, evidence in support of this concept has steadily accumulated but it has been stongly resisted by most biochemists and molecular biologists. Opposition is even stronger among scientists in other fields and in the general public thanks to a steady stream of anti-junk articles in the popular press.

Much of this opposition to junk DNA stems from a massive publiciy campaign launched by ENCODE researchers and the leading science journals back in 2012.

It's likely that most of the controversy over junk DNA is related to differing views on evolution and the power of natural selection. Most people think that natural selection is very powerful so that modern species must be extremely well-adapted to their present environment. They tend to believe that complexity is simply a reflection of sophisticated fine-tuning and this must apply to the human genome. According to this view, the presence of huge amounts of DNA with an unknown function is just a temporary situation and in the next few years most of this 'dark matter' will turn out to have a function. It has to have a function otherwise natural selection would have eliminated it.

The gene's-eye view of evolution

I'm reveiwing some of the contributions to Evolutionary Biology: Contemporary and Historical Reflections Upon Core Theory. In this post I want to cover Arvid Ågren's contribution on the gene's-eye view of evolution.

Ågren starts out by reminding us that Richard Dawkins' book The Selfish Gene was voted the most influential science book of all time in a 2017 Royal Society poll. He goes on to say,

Regardless of one's views on the poll results—or the book's argument—the far reaching sway of The Selfish Gene means that anyone interested in the history and future of evolutionary theory has no choice but to grapple with its ideas. Chief among these is the so-called gene's-eye view of evolution. This is the approach to biology originally introduced by George Williams in Adaptation and Natural Selection and elaborated and popularized by Dawkins, that it is the genes, and not organisms as Darwin originally envisaged, that deserve the status as the unit of selection in evolution. Emerging in the decades succeeding the Modern Synthesis, the gene's-eye view of evolution has become an emblem of orthodoxy in biology.

Why Trust Science?

Bruce Alberts,¹ Karen Hopkin, and Keith Roberts have published an essay on Why Trust Science.

In this essay, we address the question of why we can trust science—and how we can identify which scientific claims we can trust. We begin by explaining how scientists work together, as part of a larger scientific community, to generate knowledge that is reliable. We describe how the scientific process builds a consensus, and how new evidence can change the ways that scientists—and, ultimately, the rest of us—see the world. Last, but not least, we explain how, as informed citizens, we can all become “competent outsiders” who are equipped to evaluate scientific claims and are able to separate science facts from science fiction.

Most of the essay describes an idealized version of how science works with an emphasis on collaboration and rigorous oversight. They claim that the work of scientists can usually be trusted because it is self-correcting.

What is photosynthesis?

A recent commentary in Nature prompts me to revisit an old bugaboo. The commentary discusses some recent work on CO₂ fixation in plants [A genetic switch drove photosynthesis in plants¹]. It begins with,

Photosynthesis, which uses energy from the Sun and carbon dioxide from the atmosphere to create carbohydrates, might be the most influential set of biochemical reactions on the planet.

Here's the problem. That's not a very good definition of photosynthesis. I discuss a much better definition in a post from seven years ago: Scientists confused about photosynthesis. A better definition is that photosynthesis is the process by which light energy is captured and converted to chemical energy. The direct products of photosynthesis are ATP and reducing equivalents such as NADPH. These cofactors are used to drive all sorts of reactions in the cell including DNA synthesis, protein synthesis, lipid synthesis, and carbohydrate synthesis.

This is very obvious when you examine photosynthetic bacteria but, unfortunately, photosynthesis was initially studied in large plants where much of the chemical energy produced by photosynthesis is used to fix CO₂ and make carbohydrates. This led to the widespread belief that photosynthesis is all about making carbohydrates.

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1. I'm using the title from the printed version of the journal. The web version has a different title. (I don't know why.)