Saturday 13 June 2015

Second part of a review of 'Demain, les animaux du futur' (Future evoluton from France II)

In my first review of the book 'Demain, les animaux du futur' I gave an overview of its contents; this second part will provide a broader view.

I have just spent a pleasant day in Paris with the authors of the book, Marc Boulay and Sébastien Steyer, mostly to talk shop. Their book is doing well, and is the best-selling book at present in the nature category in France. Accordingly, the authors are being approached to give interviews quite often. In fact, while we were at Sébastien's place of work, the Muséum National d'Histoire Naturelle (National Natural History Museum), a journalist showed up from Science et Vie. This magazine is in scope probably the closest equivalent in France to Scientific American. Some of the earlier comments on the book also touched on topics that came up in the interview, such as whether the 10 million years that passed from the present to the time depicted in the book are long enough to account for some of the profound changes in body size, shape and lifestyle to have occurred. To answer that, let's have a look at some of the changes the authors envisaged.

Click to enlarge; Copyright Éditions Belin
Ten million years from now, according to the book, giant bats have emerged from the night, so to speak. They are active in broad daylight and have lost three of their five fingers, which makes them look somewhat like pterosaurs. The wingspan of the largest species, Gigapterus tropospherus, shown above, reaches 15 meters for males. This species has dark spots on its wing that help the animal soak up sunlight during the day to use at night or at high altitude. Mind you, the text states that energy is stored through melanocytes, so this is not photosynthesis, just light and hence to a large extent also heat.

Click to enlarge; copyright Éditions Belin
Another instance of rapid evolution is Benthogyrinus giganteus, an amphibian filling the niche of present-day baleen whales. Compared to its present days amphibian cousins it is absolutely gigantic, even longer than a blue whale. It thrives in the seas, something no present amphibian does. The authors are quick to point out that past amphibians like Ichthyostega tolerated brackish water, and they quote Darwin himself, who described a Patagonian frog living in water too salty for humans to drink. But perhaps its most intriguing feature is that the animal is basically a giant tadpole, meaning it is a larva. It procreates as as larva, in contrast to normal tadpoles that have to metamorphose into adult frogs or toads to do so. This process of retaining juvenile characters in adult life, 'neoteny', certainly occurs in amphibians; the axolotl is probably the best-known example. In fact, some of the peculiar traits of Homo sapiens, that's us, also suggest neoteny: compared to adult apes, we have a large cranium, small and weak jaws and teeth, little hair, etc. To my surprise the Wikipedia article on neoteny almost exclusively deals with neoteny in man. It even suggests that Neanderthal man was less neotenic than we are, so Neanderthals represent the 'adult' version of Homo sapiens more than we do. Hmm; is Homo sapiens then in fact just an adolescent version of Man, let loose upon the world without adult supervision? That might explain a thing or two, but I digress...

So how fast can evolution proceed? Some circumstances seem conducive to quick evolution. The foremost is probably a large difference between the demands posed by an environment on an animal's (or plant's) characteristics and its actual traits. If the gap is small, the eventual changes necessary for adaptation will be small too, but we want impressive changes. The required large gap can be bridged by a series of mutations each bridging a small part of the gap, provided each step conveys an advantage by itself. As an example, consider an aquatic life form faced with an enticing new and fresh world beyond the water's surface. If there is anything to be gained from foraying on dry land, such as cheap food or finding a pool that is not drying out, then a mutation that help the animal to accomplish this task will help it to compete with its fellows. A hypothetical adventurous fish making its first clumsy steps on dry ground certainly merits an epitaph such as 'One small step for a fish, but a giant leap for fishkind'. Of course, such a fumbling fish has no advantage whatsoever if dry land is already occupied by agile predators only waiting for the intrepid fish to venture its naive adventure into their territory. The best circumstances for fast evolution may therefore be a combination of, on the one hand, a large gap between demands and capabilities, and on the other hand an empty stage to stop anything impeding runaway adaptive radiation. Those are exactly the circumstances envisaged in 'Demain'.
   The empty stage in the book is the result of the 'sixth extinction', meaning the sixth time Earth witnessed an extinction of a sizeable part of the world's life forms. All were major assaults on life, and the sixth one is is the one that some authors believe we are witnessing right now. But in contrast to previous ones, caused by natural phenomena, the sixth one is caused by Homo sapiens, going about its business with reckless, perhaps adolescent, energy.
   How large the sixth extinction will be is unknown; we are probably just at its beginnings. The authors' scenario considers it to be at least equal to the mother of all extinctions, the one at the end of the Permian. But with the decline of teleost fish and almost of not all mammals, I would guess it is larger still. A nearly complete collapse of the food chains on land and at sea might indeed provide an empty stage for remnant populations to undergo quick adaptive radiation. The remnants in the book, by the way, are not random, but were mostly taken from species with near-ubiquitous representations: birds, bats and cephalopods.

Click to enlarge

Above is a photograph (of poor quality, sorry) showing, from top to bottom, Sébastien Steyer, Marc Boulay, and the journalist of Science et Vie, Elsa Abdoun. The locale is the Muséum I mentioned above, and specifically a hall showing a display of present-day whales skeletons, pertinent to the discussion. But why are whales pertinent to this particular book?

Click to enlarge; copyright where appropriate Wikipedia

Whales present a nice factual example of quick evolution. The genus Pakicetus of about 50 million years ago represents a mammal group thought to be the earliest known 'whales', but here that is a cladistic term only: you would not call this mostly terrestrial animal a 'whale' and would probably not call it 'aquatic' any more than you would call a present-day tapir aquatic. But give these 'whales' some time to evolve, and you will encounter the first fully aquatic whales, basilosauridae and dorudontinae, in the seas of 41 to 35 million years ago. What this means is that whales went from terrestrial tapir analogues to fully aquatic animals in only 9 to 15 million years, similar to the 'Demain' book's 10 million years. Of course, the oceans were not empty during this time, so whale evolution might have been even faster on a truly empty stage; even with other players around, whales exploded onto the scene.

Click to enlarge; copyright Éditions Belin

To conclude, what the book does, and does well, is to explore several biotopes. My personal preferences include what the authors did with squids, a clade also radiating to take up niches left by fish and mammals. Above is a giant one, Rhombosepia imperator. It too underwent impressive changes, including the concept that most of its tentacles fused to form false jaws, lined with suction cups. It is, as it was before, a predator, and now uses modified ink to poison its prey.
  I will not show more images from the book: it would spoil the appetite. I realise that readers would want more images, but a review should leave enough unknown for people to want to read the book (this is also the reason why I withhold new Furaha images). I really like the squid radiation, in particular the dolphin analogue 'Delphimimus jamescameroni' (Oh dear Mr Cameron, please have a look at the kind of speculative biology shown here, because it's pretty good!).

The book is not an encyclopaedia of future life; it provides no clues regarding other biotopes. That may be seen as a disadvantage; in a way it is, but I would probably have wanted more even if the book would have had three times the number of pages it has now. Knowing only too well how long it takes to produce such a work, it's perhaps just as well they stopped, to have it published as it is.