Freeman Dyson among others has speculated about the physical changes that could occur as the human species spreads into the cosmos. How will evolution deal with a colony world in a distant star system, and how long will it take before serious differentiation begins to occur? For that matter, what about the crew aboard a multi-generational starship — will humans have adapted so thoroughly to a space-borne environment when they arrive that some opt to make their planetary excursion no more than a brief research stop before pushing on to yet other solar systems?
Or will they one day adapt to the vacuum itself?
Such questions are called to mind by recent work from Virginie Millien (McGill University), whose new paper in the open source journal PLoS Biology examines islands as test beds for evolution on Earth. It has long been assumed that isolation would create selective pressures unique to an island environment. A so-called ‘island rule’ has small animals evolving into outsized versions of their counterparts on the mainland, while larger animals tend to shrink. But although systematic evidence has been scarce, Millien’s work now confirms that island species do undergo accelerated evolutionary changes in small time frames.
How small? Anywhere from thousands of years down to decades, depending on the species. But the accelerated rate of evolution tends to slow down, until for intervals over 45,000 years the difference in evolutionary rates between mainland and island species becomes statistically insignificant. The big changes seem to involve the initial adaptation. Truly remote islands show the most interesting effects, but habitat destruction on the mainland can force equally quick changes. From the paper:
The commonly proposed mechanisms that govern evolution on islands — a founder event followed by slower evolution — can be compared to the mechanisms that operate after a drastic change in the environment on the mainland. However, the present data suggest that the peculiar ecological environment on islands — lack of predators, reduced interspecific competition, resource limitation — favours faster evolution, even over several thousands of years. Species surviving in fragmented landscapes are also confronted with a modified environment characterised by a reduced area and an increased isolation relative to their undisturbed habitat. These new environmental conditions parallel those seen in true island habitats, and one may suspect that morphological changes in response to fragmentation are similar to changes in island species.
Thus evolutionary rates vary with circumstances, as we would expect. Which brings to mind some of Dyson’s speculations about the evolution of future species adapted to space itself. But a shorter range outlook ponders what could happen even on places as relatively nearby as Mars once human colonies take hold there. Millien’s work offers the possibility that evolutionary changes to, for example, differing gravitational pulls will begin to produce serious species changes in fairly short time frames. Then throw in genetic engineering for some truly interesting effects. Here’s Dyson in Disturbing the Universe:
The Mongolian nomads developed a tough skin and a slit-shaped eye to withstand the cold winds of Asia. If some of our grandchildren are born with an even tougher skin and an even narrower eye, they may walk bare-faced in the winds of Mars. The question that will decide our destiny is not whether we shall expand into space. It is: shall we be one species or a million? A million species will not exhaust the ecological niches that are waiting the arrival of intelligence.
And a bit later:
When life invades a new habitat, she never moves with a single species. She comes with a variety of species, and as soon as she is estabished, her species spread and diversify still further. Our spread through the galaxy will follow her ancient pattern.
The above quotes are from my 1979 hardcover edition of Disturbing the Universe (New York: Harper and Row), both on p. 234. Millien’s paper is “Morphological Evolution Is Accelerated among Island Mammals, PLoS Biology Vol. 4 Issue 10 (September, 2006). And although I don’t have time to get into this today, the open access movement which PLoS Biology exemplifies is part of an ongoing revolution in science publishing that we’ll continue to examine in these pages.
I’m not an evolutionary scientist, but I am a biochemist. I think evolution that leads to speciation among humans is a little more difficult to guage because in an increasingly tolerant world (hopefully) individuals are far less likely to select against mates that are physically different (but can still mate resulting in fertile offspring).
There’s at least one study that I am aware of concerning birds around the Himalayas (Warblers) that biologically can have offspring, but never mate because of changes to their mating songs/calls –compare this to cultural differences amongst humans.
http://www.nature.com/nature/journal/v409/n6818/abs/409333a0.html;jsessionid=984EDBCCD9DA2BE93F3A33169AB993A7
The point being that if we assume that future humans don’t discriminate between breeding partners, groups that are separated for long periods of time (but not “too” long) may still choose to interbreed and thus be one species. Perhaps a species that has many different outward phenotypes… if we compare these hypothetical future humans to something like Breeds of Dogs. Perhaps some are more compact for a particular environment, or some have developed lighter bones, etc… but essentially, all are still the same species.
The second point I would like to bring up is with regards to the budding/expansive field of small RNAs; specifically microRNAs. It is quite possible that quick/sudden evolutionary changes may be initiated through changes to these microRNAs since one current (and widely held) hypothesis is that as a whole this class of small RNAs are vital during development.
It is possible that mutations affecting when or how strongly a microRNA is expressed/functions could serve as a driving force for physical evolution/adaptation to an environment. This (for example) could affect a body in a number of unexpected ways, perhaps affecting the size of the organism or even the amount of hair, the size of an organ, how developed the brain is, etc… And with the mutation being in the microRNA instead of the protein(s) that the microRNA regulates, an organism could develop very differently while no protein has been modified in anyway. Of course, this is hypothetical, but there is some very nice biochemical work floating around…
I think there may be some new ideas about evolution and adaptation coming forth in the not so distant future due to recent research.
-Zen Blade
All very interesting, but I think one important point tends to be overlooked, when talking about future changes in a (human) species: a species will only change over time, provided that selective pressure is exerted, favoring certain varieties in the population, plus isolation. If advancing human technology permits the same human variety to survive in very different environments, there will be no selective advantage, no biological adaptation and no speciation. Only if certain traits allow better chances for survival (and better reproduction), will they prevail in a poplation. It is very well possible that advancing technology and increasing communication will together actually work against biological adaptations, rendering them unnecessary.
Paul;
For a humorous twist on this, I’ll send you a 1-page fictional piece I did about the evolution of humanity once out there. Only post it if you think it adds value.
Fine article. The idea originates, however, with J. B. S. Haldane and Olaf Stapledon, who were the first to speculate on the adaptation of humanity to extreme space conditions back in 1920s. However, the ironic twist is that in the long run, too much adaptation can kill you – if you wish to retain your intelligence, that is! Namely, you get too specialized, you become to solve all challenges by evolutionary developed specific mechanism, not by cogitation and problem-solving using culture and technology. In the course of hundreds and thousands of generations, this would lead to speciation of humanity into very specialized and less and less intelligent (in both the vernacular and the SETI-interesting sense) species. This ironical speculation has been nicely portrayed in “Permanence”, an SF novel by Karl Schroeder, although it has some precursors in Stapledon, paleontologist David Raup and some other sources. I’ve written a brief piece on it last year in JBIS (Journal of the British Interplanetary Society, vol. 58, 62-70 (2005)) with some more discussion of this option. Not an immediate worry, in any case (we have waaay more pressing things to worry about)!
I really enjoyed Schroeder’s novel Permanence. For those recently joining our discussions, Centauri Dreams talked about both Schroeder and Milan Cirkovic’s ideas in a post about a year ago, with URL here:
https://centauri-dreams.org/?p=102
Cirkovic’s JBIS piece is well worth seeking out if you’re near a good research library (and how I wish JBIS had a more active online presence!).
…and of course there’s the example of the Moties in “The Mote in God’s Eye” by Niven and Pournelle.
Some subspecies are intelligent, some are less so.