On the end of species

Working through my synopsis of Darwin’s On the Origin of Species got me thinking about how things have changed since it’s publication. We now have unprecedented access to the blueprints of life. Genetic technologies are changing how we view living things, but might they even begin to dissolve the very meaning of a ‘species’?

Traditionally, species have been discrete ‘types’. There were infinite forms that could exist, as a result of Nature’s playful creativity and God’s genius, but they were discrete, and stable. They had been gathered up on Noah’s Ark in pairs, ordered in the heirarchical Great Chain of Being that structured the world. There might be the odd monstrous hybrid form disrupting taxonomies, such as an armadillo- the lovechild of the tortoise and hedgehog looking for ways to spice up their long confinement on the Ark – but such things did not change the fact that there were a divinely designed set of types in the world. The could be ordered by Man, if only he could be ingenious enough to understand God’s plan.

Great_Chain_of_Being_2-2
The Great Chain of Being, 1579 drawing from Didacus Valades, Rhetorica Christiana

Most people still see species in this way, as relatively separate, stable kinds. In biological terms, species can be seen as ‘peaks’ in a genetic landscape, isolated, interbreeding populations adapted to specific niches. These peaks have been created by natural selection, building up sets of genetic forms that help adapt a group of organisms to a particular environment, but simultaneously make it very difficult for them to interbreed with other populations or climb across to other peaks. Trying to do so produces offspring that are just not going to do very well.

Visualization_of_two_dimensions_of_a_NK_fitness_landscape
Visualisation of an NK fitness landscape. The arrows represent various mutational paths that the population could follow while evolving on the fitness landscape.

Discoveries such as the mutable nature of microbial lifeforms have shaken this view of ‘neat’ and distinct species. Quite simply, most life on Earth is microbial, of which we have only the first glimmerings of this abundance. Microbes don’t play by the rules. It’s life, but not as we like to imagine it. They reproduce asexually, clonally, but can transfer genes between them and don’t stick to the ‘seperate breeding groups’ definition of species. They evolve at incredibly rapid rates and essentially structure the global ecosystem, but we know amazingy little about these miniature powerhouses, who’s family trees more than dwarf our own.

tree-of-life-2016-2.jpg
The current Tree of Life (Nature.com)

Rapidly-developing genetic technologies, such CRISPR gene editing, are dissolving these boundaries further. An increasingly-fragmented picture of species-as-gene clusters is emerging. These clusters dont need to stay together: their components can be patented, removed and bolted on to each other to make genetically hybrid organisms. The prospect of individual genotyping already shifts the identity of the individual: already, we can purchase a commercial genotyping service to tell us our susceptibility to diseases and other predispositions. In the future, just as we can now edit bodies’ appearances and even biological sexual functions, we will likely start to edit our own genomes.

The next creatures up for ‘de-extinction’ will be the Australasian moa birds (Dinornithiformes). The 9 species of these avian behemoths roamed New Zealand’s forests until about 600 years ago, but we still have their ‘ancient DNA’. Parts of the moa genome could soon be resurrected in living organisms, just as ancient mammoth DNA is being worked into Asian elephant genomes.

Moa kiwi photograph

These de-extinction projects involve partial genomes: a ‘mammoth’ or moa is to be resurrected through token genetic elements, fragments salvaged from specimens. The creatures themselves can never be brought back. Genes are being revived, not the animals themselves. If we start to create ‘mammophants‘, ‘mostriches’ and other revenants, will we impose a kind of artificial selection on these creatures, deciding which genes make something ‘mammothy’ or ‘moa-like’, just as we create new, useful transgenic organisms?

Genes continue well beyond the individual or species that contain them, while environmental effects can rapidly shift the way genes and genomes function. At a time when species are disappearing at an unprecedented rate, might the perservation of the gene become prioritised above the conservation of whole genomes or phenotypic forms?

We already emphasise genes and genetic diversity when creating seed banks, and genomic libraries might become the last resort for preserving species bound for extinction. But these persepectives are a big shift from the zoo-based or in-situ whole-organism conservation that has hitherto been practiced. As well as an anthropogenic mass extinction, are we going to see the dissolution of the idea of the species itself?


 

dodo rose

 

© Natalie Lawrence: The Manticore 2018
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