Dec
19
How did poisons become the preferred means of predatory snakes to kill mammals and birds?
By
Can natural selection explain the origin of poison for killing one’s prey. The snakes (and all reptiles) preceeded birds and mammals on the evolutionary scale of complexity. That being the case, how is it possible that it developed the ability to kill mammals and birds with poisonous bites? What is the specific mechanism that would explain how snakes, presumed to be earlier on the evolutionary timescale, develop poisons as a way to kill for food, and develop the substances necessary to enable them to eat and digest the birds and mammals, animals that came into existence much later on the timescale?
5 Comments
December 19th, 2009 at 4:55 am
it’s called evolution. obviously it’s the most effective way for them to kill. poisonous animals are usually small. they need poison to overpower they’re prey.
December 19th, 2009 at 5:22 am
Yes, it is natural selection. The venom is modified saliva, which has been selected for over many years.
December 19th, 2009 at 5:59 am
snakes do not only feed on birds or mammals. They also prey on other snakes, fish, reptiles, insects, etc. And venom is not the only way they have to secure a meal. there are also constrictor snakes that kill by suffocating its victims.
Natural selection has a lot to do, and snakes have evolved, as most living things, according with the ecosystem they live in and in relation with the animals they feed on. Some have hollow fangs, others have fangs with an exposed venom groove, some have the fangs located at the back part of their mouths, some of their poisons are highly toxic or fatal to humans, others only represent little harm, but altogether, venoms -together with their snakes-, have adapted and not necessarily were meant in the begining for birds or mammals.
December 19th, 2009 at 6:15 am
First off: THERE IS NO SUCH THING AS AN EVOLUTIONARY SCALE OF COMPLEXITY. The idea that the beings can be ordered from bacteria to human belongs in the 18th century.
There were both birds and mammals around in the Mesozoic Age, when snakes evolved. And the first snakes were similar to boas, not venomous ones; the colubroids (the group that includes the venomous forms) are first recorded in the Miocene (that is Tertiary, long after the diversification of modern birds and mammals). Therefore, you are starting from a false premise.
Also, salivary glands are present in all tetrapods, and especially in amniotes (reptiles, birds and mammals). Saliva possesses enzymes, and it’s not that difficult (from a biochemical or evolutionary viewpoint) that any mutations that changed those enzymes into other more toxic ones were retained because of their advantage when subduing prey. Indeed, the evolution of venomous saliva did not happen once: Gila monsters and at least some insectivorous mammals also have similar (but independently evolved) systems.
Thus:
- snakes did not precede birds and mammals
- poisons are made of enzymes, and all enzymes can be “poison” to some living being or other (ask the bacteria that are killed by the saliva in your mouth!)
December 19th, 2009 at 6:44 am
Well, first off, poisons are not the “preferred” means for snakes to kill (all snakes are predatory), they are actually one of the rarer means. More snakes kill by constricting their prey or simply by overpowering it than by poison.
Also, snakes are more recent on the evolutionary scale than many other reptiles. Obviously, reptiles didn’t cease to exist when birds and mammals evolved, and some of those reptiles continued to evolve into more and more niches. Snakes are one example of that, they are far more recent than things like alligators, which have been in pretty much the same state since the age of the dinosaurs. Some snakes still have vestiges of their back legs, called “spurs.”
And last but not least, it is a misunderstanding that evolution happens in a linear fashion (i.e. that the creatures that evolved most recently are always the more “advanced”). Instead, it happens in branches, some newly evolved creatures die out when the conditions that favored their adaptations change, while others (such as crocodiles) are more ancient yet better suited for survival through changes. Also, when creatures evolve, they can’t be immune to every single possible predator, that’s simply impossible. There will always be something that’s stronger than you even if you’re smarter, or small enough to escape you no matter how big you are, or poisonous enough to kill you if you can’t fly away in time.