Convergent evolution... tell me more
Use the following menu to navigate through this text:
- What is evolutionary convergence?
- Universal convergence
- Concerted convergence
- Convergence and optimality
- Detecting convergence
- Do you mean convergence, or should we say parallelism?
- Is there a General Theory of Biology?
- The search for extra-terrestrial life
The search for extra-terrestrial life (and intelligence)
The ultimate test for the significance of convergence will come from the exploration of alien biospheres. Our prediction is that in many cases apparent differences will be very much skin-deep. This is suggested by the innumerable examples of terrestrial convergence, brought about by the constraints of unalterable physical and chemical laws. Such convergences even occur between surprisingly disparate types of animal, for example the tentacle of the octopus can operate astonishingly like a lever arm with joints, just like the arms we possess as vertebrates (Sumbre et al. 2005).
Life on un-Earthly planets
When hypothesizing the nature of alien biospheres we can allow for quite radical differences in such parameters as atmospheric density and composition, strength of gravity, depths of oceans and ultra-violet flux and still make some very good first approximations as to the life forms we might expect to find there. Certainly in what to us will be extreme planets, say with a global ocean a hundred kilometres deep or much larger rocky planets with extreme gravity, our extrapolations will be tentative, but we can certainly manage to envisage life in a range of habitats considerably wider than the Earth.
Astrobiology and the Fermi Paradox
As the study of convergence may feed predictions about the nature of alien biospheres, it should be an important part of astrobiology. Indeed, the very ubiquity of convergence begs a particular question when it comes to convergence in tool making, music, technology and cognitive systems. If existing here on Earth, then why not anywhere else? If we assume that convergences such as tool use and specialised cognitive systems (which can be treated as general biological properties) are the necessary pre-requisites for the emergence of advanced human-like characteristics, and if in addition convergence is indeed a universal rule of evolution, then clearly something seems to be missing. Here, of course, we touch on the Fermi Paradox, the “Where are they?” question, originally posed by the great Italian physicist Enrico Fermi. After all, if convergence is ubiquitous and includes the emergence of advanced sentience, combined with the fact that many potential solar systems are billions of years older than ours, then it seems very surprising indeed that we have no evidence of advanced extra-terrestrial activity. Are the patterns revealed by convergence false? We don’t think so. Is the Fermi Paradox one of the biggest questions in science? We suggest that it is.
Please note: words or phrases shown in bold in the PRINT VERSION of this text normally indicate hyperlinks on the webpage.