I recall hearing of some mamal where one branch of the species lost its social group instincts (I think due to the environment losing the larger prey it needed to coordinate to capture). Are there many examples of evolution going towards simplicity? I always get the sense that evolution leads towards increasing complexity; for instance in primate brains…have some species lost gains “made” in the past (gains = more complex behaviors). If not, is this because complex behaviors are usually more adaptive? If so, again, does this mean evolution pushes towards rising complexity? If that makes any sense…
Well, the elaborate joke of the band Devo was that this is happening to human beings right now. Twenty-five years after the band’s heyday, I’m not so sure it turned out to be a joke.
Evolution is random. It does not push toward any goal.
As for your example, I believe there are moles with non-functioning eyes.
The process of domestication has created “dumber” versions of some species–turkeys and irish setters spring to mind.
But in those two cases, natural selection has been substituted by human selection.
Apparently some various groups of homosapiens (or one of the more-advanced species) devolved, having no need of their abilities with tools and verbal communication.
I can’t recall where I read this, what the specifics were, or how they determined it.
An animal or plant – any animal or plant – loses those capacities it no longer needs in order to survive. E.g., we probably could synthesize some of our vitamins, as other animals do, but with them available ready-made in our diet, we didn’t need to. So there was no selection for retaining the ability, and the freed-up gene might mutate, including to something useful, selecting against it.
For a fascinating discussion of what “degeneration” actually means in evolutionary terms, read Stephen Jay Gould’s “Triumph of the Root-Heads.”
I dunno if “backwards” is really an apt description, but there are hundreds of species which have lost certain abilities through evolutionary forces. Flight is one of the most common. There are dozens of birds which through forced isolation - like, but certainly not limited to, the break up of proto-continent Gondwanaland - have lost the capability of flight held by their predecessor species. And the same goes for hundreds of insects.
David Quammen’s book Flight of the Dodo on island biogeography explains this phenomenon marvelously.
It has also been postulated in At the Water’s Edge by Carl Zimmer (another fascinating and remarkably well written book) that whales evolved from land creatures; that is, land mammals originally developed from ocean-going species, splintered, and some of them went back to the ocean, whales among them.
Is this the sort of thing you have in mind? Incidentally, it came as news to me that the worm lizard is apparently no longer considered part of the suborder Sauria (lizards)
Well, humans have lost the acute sense of smell, for example. Are we evolving backwards?
Any talk of this kind presupposes a ‘goal’.
Survival of the fittest. Fittest meaning best adapted, not ‘smarter’.
Humans now have a vestigial appendix.
Things that may appear to be “backwards” evolution (a meaningless phrase, but whatever) are often - in fact, let’s say usually - actually just continuing evolution to make the organism more fit for its environment. Things like flight and eyeballs take energy to create and maintain, so there are costs that go along with the benefits. If an organism adapts to an evironment where the benefits no longer outwiegh the costs, it’s better off dropping those traits. Why spend the energy building a couple of eyeballs if you’re never going to use them? Why maintain huge flight muscles if you don’t need to take to the air to escape predators?
I would consider “backwards evolution” to mean an organism is becoming less able to survive in its environment. Obviously, if this happened, these critters wouldn’t survive as well, and would die off and be outcompeted by their more fit cousins. So we don’t really see it.
Speak for yourself. My appendix is the root of my magical powers.
Yes, almost all of them. Given equal starting parameters evolution selects the most elegant solution capable of survival. As a result the general trend is towards simplification. Mammals for example have notably smaller genomes, and concomitantly fewer proteins, than our amphibian ancestors. The same is true of flower plants WRT pteridophytes and similar plants. The general evolutionary trend has always been towards the simplest possible solution. The actual number of cases of evolution unambiguously producing greater complexity is fairly small.
In general exactly the opposite is true. Extraneous traits are rapidly trimmed through use-it-or lose it, and the more fine-tuned an organism is to a specific environment the fewer traits are likely to be beneficial.
Yes, but you can’t look at an organ in isolation and talk of evolutionary complexity in any meaningful way. Evolution works on individuals and is manifested in populations. Individual organs are just a sideshow. The human brain is complex, but it is complex because our senses and our gut are far more simple than our immediate ancestors, or vice versa depending how you want to look at it. By any objective standard (eg kg for kg or gene for gene) humans are less complex than our ancestors. The same applies to primates generally WRT the carnivore type ancestor. Larger brains, but concomitantly reduced senses etc.
That’s’ the whole process of natural selection for you. Large brains can only be selected for it they enable more energy to be harvested in some way, which means that the organs for harvesting that energy become superfluous and are reduced. The same goes for any other apparent increase in ‘complexity’ in specific organs, or systems or behaviours. It’s almost invariably traded off against a reduced complexity elsewhere.
Billions of times. Tetrapods after the amphibians all lost the larval stage that had been gained by some of the earliest multicellular life. That’s massive loss of an extremely complex behaviour. Mammals lost the behaviour involve din burying eggs in warm sand or decaying leaf litter, another major behavioural loss. But as you can see in both these cases we tend to think of the new models as being more complex, not less. Yet that’s not objectively the case.
Everything is adaptive if it’s the result of evolutionary selection. I it had no adaptive advantage it wouldn’t be selected for. ‘More’ adaptive is an essentially meaningless term, either trait is adaptive or it ain’t. Suckling for example is pretty simple behaviour, it only involves a handful of muscles. Yet it is no less adaptive than speech or tool use. If a human lacked any of those behaviours they would die in the ‘natural’ world.
It doesn’t really make much sense. Evolution isn’t directed, it doesn’t push towards anything but reproduction. If there is a general trend then it appears to be towards more elegant forms and lower complexity. Half-arsed solutions like terrestrial tetrapods spending their first few weeks as fish get tinkered with to produce more elegant solutions, first self-contained eggs and then live birth. As any engineer or computer programmer will tell you, half-arsed solutions are usually far more complex because they have to do a lot of things that aren’t really necessary. Evolutionary changes tend to be the same. Evolution produces solutions that work, not solutions that are ideally engineered. But the selection process itself means that non-essential steps tend to get trimmed off. As a result the general trend is towards more elegant and hence more simple solutions.
And a degenerate prehensile tail. And what’s with facial hair? Et cetera.
It’s true that phenotypes often degenerate when unneeded, but this is hardly “evolving backwards”. What transpires is that the species no longer needs to spend the energy on a characteristic to best fulfill its evolutionary “goals”, i.e. reproduction. In the case of filghtless birds, for instance, the species have eschewed the costly expense of musculature and skeletal components to support flight (not to mention the high calorie diet to maintain sufficient energy for flight) for a niche that allows them to remain aground. One is not “better” or more progressive than the other in any overall sense; it’s just a matter of selection for the local environment (food sources, defense from predation, and so forth).
The only way a species could truly be said to be “evolving backwards” is if their genetic coding actually returned to a former state, a circumstance so astronomically unlikely as to be dismissed out of hand. It’s somewhat overreaching, or at least dubitable, to suggest that genetic mutation and alteration is strictly random–different nucleotides demonstrate various rates of defect–but it is highly unlikely that thousands of alterations in the gene sequence would be undone, in order, by natural action and variation alone.
There are attempts to “reverse select” for extinct species like the attempt to recreate the Aurochs, an extinct precursor to modern domestic cattle and oxen. However, the goal isn’t to reproduce an animal that could breed true with the aurochs, but rather create a new species that demonstrates the characteristics and phenotypical expressions (called atavisms) of the original animal.
In some ways many domesticated species–dogs, chicken, pig–demonstrate a degeneracy to the infantile or immature state. Domestic dog puppies, for instance, quite resemble wolf cubs, but whereas the cubs will grow up to demonstrate protruding snouts, large erect ears, deep set eyes, and other characteristics that suit them well for survival in the wild, the dog will retain the more puppish characteristics, presumably because their human masters (or perhaps better considered as partners) find them cuter, easier to control, or otherwise better suited to domestic activities. (Although it should be noted that working and primative dogs like shepherds, spitzs, and dingos tend to retain significant wolf-like characteristics, while the sporting and non-sporting breeds more typically demonstrate infantile phenotypes.)
But as others have pointed out, there is no real “backwards” in evolution by virtue of having no reference “forwards” to measure against. Natural selection allows the animals (and the genes that define their characteristics) which are best suited to a place and niche to propagate most successfully until such a time that selective pressures change. And there is no “top of the food chain”, either; we might think that our ability to build cities, wage wars, and walk into a Ruth’s Chris and order a Kansas City Strip rare on demand makes us superior to the rest of the animal kingdom, but in the end we’re just dinner for single-celled anaerobic bacteria.
O mighty Caesar! dost thou lie so low?
Are all thy conquests, glories, triumphs, spoils,
Shrunk to this little measure?
Stranger
Not that it detracts fom your point, but apparently it has happened, or as far as we can tell. If the genetic code hasn’t returned to its former state (and we can’t know) then it has returned to a state that is functionally identical.http://news-info.wustl.edu/tips/2003/science-tech/walkingstick.html
How about various parasites, such as tapeworms? Are they forms that once had the ability for living independently but have lost it?
In case anyone takes this seriously, there is no evidence of this sort of thing happening. I don’t know what “one of the more-advanced species” means, but this is not true of us (Homo sapiens) or any of our hominid ancestors.
Quite often yes. But don’t get the idea that this is as it appears either. A tapeworm might have a much simpler gut compared to a free-living flatworm , but it has an infinitely more complex lifecycle and some complex tricks for evading the host immune system. On the whole the parasite may be simpler, but what you think you see is not what you get.
The problem is that it’s hard to define complexity in any meaningful way. The few objective methods we might be able to come up with probably suggest the parasite is impler, but that doesn’t mean that it is simpler.
No doubt. Parasites might easily pay dearly in other physiological aspects for cadging a living off a host. The OP did define “evolving backwards” as “away from complexity and toward simplicity.” The tapeworm’s simple life of hanging on, feeding on stuff its host sends and producing eggs could very well be more complex overall than that of the wolf or any other mammal.