The two-headed snake was the result of two monozygotic twins failing to separate. In the wild two heads are not better than one because they tend to make different decisions that will affect the animal’s survival odds.
What amazes me though is the fact that although they seem to be “mere” beasts, the two snake heads learn to live together. It is as though the two reptiles knew that attacking each other would undermine their own chance to flourish.
Many of the aggressive, mindless decisions humans make are blamed on our reptilian brain, but in this case the reptile’s brain seems to be more profound than it is typically described.
When I was on Maui in 1991, a 2-headed snake was found there. It was named “Thelma and Louise” and taken to a local zoo. The human counterparts, Abby and Brittany Helsel, now 30yo, have a remarkable ability to work together.
Here’s a video made by some snake breeders, and they had a baby snake with two heads and a single lower jaw. They realized pretty quickly that it couldn’t eat, so they had it euthanized. You can see it about 2, and 5 1/2, minutes in.
Don’t underestimate the role of chance and selective bias. You did not get to hear about the two headed snakes that did attack and kill each other, or starved, or were attacked by predators while they argued, early in their lives.
It is a more complex situation than just two equally connected heads. During development in egg or womb, there may be unequal development of nervous pathways. One brain may develop more sway over control of the nervous system. The second brain may be fully functional, but not as fully wired in. There is a whole system of unconscious brain functions that regulate vital systems to live. I don’t think you can have two brains taking the time to argue out when it is time to beat your heart or take a breath, etc…
I suspect that in the case of the two headed snake. One head may be almost fully functional, but not even 50% in control. Along for the ride mostly. Where is the adrenal gland in a snake? Do both heads have one? Then it might be a bonus. One head sees a threat and adrenal gland pumps out, run for it! But what does the second head make of that? I do think that a two headed animal, will have a very dominant head. With the second head/brain, being a source of confusion most of the time.
It really depends on all the pathways and subsystems that are controlled or not. I suspect that a successful two headed animal has a very dominant biologically connected head, and a passenger head that is just along for the ride. As separate as any two individuals in thinking. But connected in feedback from the common body. Interesting. The dominant head can experience fight or flight experience, while the other may not notice the event till the bodily chemicals flood it’s brain. Oh, we are running for our lives now. Or the not dominant one sees danger, but cannot make itself run.
@Kedikat, I think you’re thinking of the pituitary gland, not the adrenals. The adrenals are (as the name indicates) on top of the kidneys, and while a snake’s innards aren’t exactly the same as a mammal’s, I doubt they keep their kidneys in their skulls.
But I don’t know how much of a role the pituitary plays in fight-or-flight response, and it’s mostly associated with growth hormone. Too much pituitary activity usually results in unhealthily-large amounts of growth.
The hypothalamus in the brain is connected to the pituitary and plays a role in antipredator defensive behavior. As in most vertebrates, a snake’s adrenal glands are above the kidneys, located within the body.
Most of the examples of two-headed snakes (like other two-headed reptiles) seem to be young individuals, and often ones born in captivity. While they may be able to survive for a while, I doubt many manage to survive to adulthood in the wild.
I might speculate that a two-headed snake might have it somewhat easier than a two-headed lizard or crocodilian, since it wouldn’t have to coordinate the operation of its limbs based on two separate visual systems, but I don’t know if that is the case.
The more I think about it, the more questions I have about this. Didn’t snakes once have legs and doesn’t their slithering system use most of the same muscles as their legs did? Its very possible they have the same issues but can’t show them due to not having visible legs.
I’m totally not arguing with you, I’m just thinking this could be an interesting out shoot of the heads thing. Its OK if you tell me that I’m a dumbass and should go play somewhere else, I have zero credentials and only a small amount of web based info about it.
Yes, ancestral snakes did have legs, but except for boas and pythons and a few other primitive forms (which retain traces of the hind leg bones) they have lost all trace of the bones and muscles of the limbs. Their locomotion relies on their belly muscles and is entirely different from that using limbs.Basically they “walk” using the tips of their ribs. That’s going to be simpler than having to coordinate a set of four limbs.
