The legendary scientist Jane Goodall came through my town recently and made headlines by talking about the dangers of genetically modified organisms, in her words, a “shocking corruption of the life forms of the planet.”
“We’re poisoning the land, we’re poisoning animals, and I truly believe we’re poisoning ourselves,” Goodall told reporters at a press conference she arranged during her visit to Salt Lake City.
What a letdown.
Goodall’s groundbreaking contributions to the study of animal behavior and wildlife conservation inspired me as a kid. Her great 1986 book “The Chimpanzees of Gombe” was a moving, wise and scientifically rigorous testament to the power of close observation of the ways of individual animals. I hadn’t kept up with Goodall’s recent exploits as an anti-GMO crusader. Her critique, I’m not happy to say, is shallow and rooted in the same naive intuitions that shape so much thinking about recombinant DNA among non-scientists.
The key misleading intuition I’m thinking about has a technical name: psychological essentialism. It is the gut feeling that each living thing, species and individual, must have an immutable core that shapes its identity. DNA has captured the popular imagination as central to that immutable core. Some have argued that this makes our minds highly receptive to suggestions that the manipulation of DNA is contrary to nature, horrific and dangerous.
But the essentialist intuition isn’t a reliable guide. Biological boundaries are blurry. Species do not have immutable cores. Gene swapping from one species to another did not begin in a laboratory. From the beginning, living things on Earth have promiscuously exchanged DNA elements across the not-so-fixed boundaries of species, phylum, order and kingdom. Transgenic organisms are all around us, and they were here, naturally, long before the science of molecular biology and the business of Monsanto.
One of the most widely eaten foods in the world, the sweet potato, carries DNA elements that jumped from bacteria thousands of years ago. The function of the DNA isn’t yet known, but one bacterial gene in particular appears to be present – and active –in all cultivated sweet potato varieties. It’s not found in closely related wild relatives, which suggests that the bacterial DNA codes for a valuable trait that ancient farmers selected for during domestication around 5,000 years ago in South America. Agrobacterium species, the microbial family that donated DNA to sweet potatoes, have long been known to transfer DNA elements to plants they infect, and most GMO crops are developed using agrobacterium strains to shuttle foreign genes into target plants.
All ferns are GMOs. They thrive under low-light conditions with the help of a highly efficient light receptor that the common ancestor of all ferns picked up in a gene transfer from the lineage of hornworts, moss-like plants lacking seeds and vascular tissue. The bryophyte light receptor, called neochrome, combines a red-sensing protein and blue-sensing protein into one unit capable of capturing energy across a broader spectrum of sunlight. With it, ferns occupied a vast niche in the understory of forests.
The alga Galdieria sulphuraria, a resident of boiling, poisonous volcanic hot springs, adapted to its harsh environment by taking a slew of genes from the first colonists of those hellish waters: bacteria and archaea. By one estimate, more than 5 percent of protein-coding genes of G. sulphuraria were acquired from microbes, equipping the algae with tools for detoxifying heavy metals, taking in carbon sources, and diversifying energy metabolism.
Naturally transgenic organisms can be found in the animal kingdom, too. The common pea aphid is the only animal known to have the ability to make its own carotenoids, compounds that serve a lot of important roles: light detection, oxidation control, immune system modulation, body coloration. While other animals must glean carotenoids from food, the pea aphid acquired its own set of carotenoid biosynthesis genes from fungi, organisms on a far distant branch of the tree of life, probably one of the symbiotic strains of fungi that live within aphids. The fungal genes have allowed pea aphids to evolve alternate red or green body colors that help them hide from attackers. Red forms can better evade detection by parasitic wasps while green forms are less visible to predatory ladybugs.
Mosquitos seem to have incorporated at least two genes from bacteria that live in their guts. It’s not yet clear how the genes, taken from wolbachia bacteria, serve mosquitos but the two genes are active in the insects’ salivary glands. And they are present in distantly related mosquito species, which suggests they’ve been retained for a purpose for many thousands of years.
All jellyfish, sea anemones, corals and other cnidarians owe their stinging cells, in part, to DNA borrowed eons ago from bacteria. A bacterial gene contributes to the making of an enzyme, PGA, that’s critical to the firing of stinging cells. These weapons are a core feature of cnidarians, so the borrowed DNA probably shaped the evolution of an entire animal phylum.
The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop, by Tina Kyndt and others, PNAS (2015)
Horizontal transfer of an adaptive chimeric photoreceptor from bryophytes to ferns, by Fay-Wei Li and others, PNAS (2014)
Gene Transfer from Bacteria and Archaea Facilitated Evolution of an Extremophilic Eukaryote by Gerald Schönknecht and others, Science (2013)
Lateral Transfer of Genes from Fungi Underlies Carotenoid Production in Aphids, by Nancy A. Moran andTyler Jarvik, Science, (2010)
Horizontal gene transfer between Wolbachia and the mosquito Aedes aegypti, by Lisa Klasson and others, BMC Genomics, (2009)
Horizontal gene transfer and the evolution of cnidarian stinging cells, by Elsa Denker and others, Current Biology (2008)