Can organisms evolve a useless morph or does it have to show a survival advantage?

Question

Could animals evolve a useless organ like a pineal gland, or would this have some use in the course of evolution and become redundant later?

Answer 1

All it has to do is not have a massive penalty, it can be totally useless provided that the population is not very strongly stressed or it uses little extra energy. If it's a liability it will tend to be selected against but something that's useless doesn't necessarilly put the organism in much more risk.

Answer 2

The basic requirement for evolution is that the mutations should give some advantage to the organism compared to the other organisms of the same species. This will increase the specific organisms survival and reproduction chances and all the same chances of it's offspring would again be increased.

On the other hand, there can be mutations in the history of a species which were useful at one time (as you suggested) but are totally useless after more steps in the evolution.

For example, the appendicite in the intestines is believed to be useful in digesting cellulose a long time ago, but now it is totally useless, probably after the humans became omnivorves and found it unneccessary to digest cellulose since they could find enough energy from meats.

Answer 3

The pineal regulates circadian rhythm through the hormone melatonin. In some animals, it has it's own photoreceptors, but deep within the human skull, it must respond to signals from the visual pathway.

Very often, intermediate forms have uses. To use an example suggested by another respondant, scales elongate and become primitive feathers for insulation. Short dinosaur arms may have little funtion. A thin flap of skin might appear and become useful as a cooling surface when the feathers are too warm. The surface grows to the point that gliding is feasible. The surface grows for better gliding while muscles adapt for more control. Feathers align for better aerodynamics. Finally, muscles can produce powered flight.

Answer 4

Of course they couldn't.
If an animal were to evolve a new feature it would not be selected unless if confered a survival advantage.

This is a fundemantal flaw of evolutionary philosophy.

For a reptile to evolve into a bird it would need feathers, an oil gland to provide oil for them, a new kind of lung, differently designed light bones, to lose its bladder, etc etc. Any of these on their own would likely confer a survival disadvantage. They all need to be working perfectly from the start.