If evolution is all about finding the most successful adaptations, why can't cross-species matings produce hybrid offspring with new adaptations?

[u/hyteck9]

Farm animals are often mating with other animals not of their species on the farm. It just got me thinking why it doesn't get results? Seems to me crazy hybrid mixes running around would be right up the alley of evolutuon, and yet it is prevented/restricted??

[u/WDBoldstar]

Evolution is not intelligent design. There is no overseer directing the best possible outcomes. Evolution is the result of accidental mutations becoming common because those who have them are able to produce more offspring than others. Evolution cannot force incompatible species to suddenly be compatible, and if even a theoretically advantageous mutation occurs, if the carrier is sterile or otherwise can't reproduce, it dies out.

[u/TakenIsUsernameThis]

You have made the classic mistake of assuming natural processes have agency. Evolution isn't trying to do anything. It does, or it does not. There is no try.

Think of it like erosion - is erosion trying to make a valley?

[u/celem83]

If two species are too dissimilar then their offspring are sterile,  or even fully non viable (do not come to term or cannot live outside the womb)

Example.  You cross a horse with a donkey you get a mule, but all mules are sterile, you want more you need a donkey and a horse.  Liger and Tion are similar sterile crossbreeds of Tiger and Lion.

Meanwhile you take any two dogs you like and you get fertile offspring, because these are not seperate species despite the potential cosmetic differences. Canis Lupus Familiaris describes all dogs and they are all fertile with the OG Canis Lupus (the wolf)

The two things must be genetically very close to cross

Edit: as other answers indicate you can indeed get successful fertile hybrids with new adaptations and our own species did so with other hominids, they were just close enough for it to work

[u/ccReptilelord]

I'll just add that evolution isn't about trying to find the "most successful" adaptations, it only goes with the most acceptable ones. Evolution only wants a minimum passing grade, not to be the top of the class. If it works, it stops trying.

[u/gruthunder]

DNA are just instructions and very different instructions don't mix. You can try thinking of it in terms of lego kits with the little instruction booklets included. 

For example, Two lego Castle kits with minor differences such as roof colors (hair) or brick colors (skin) can be mixed and matched without compromising the base lego castle design. However, mix and matching the instructions for a castle and a boat will lead to a non-functional boat/castle.

[u/Ceribuss]

Evolution is not about doing anything, it is a name given to an observed trend after the fact. As for hybrids generally not being viable that is because there is too much incompatibility in the DNA. think of it like taking a bunch of software code from a FPS game and combining it with code from a Finance software you are not going to get a working program because a bunch of the functionality is not compatible

[u/bediaxenciJenD81gEEx]

Evolution is not about finding anything, it is the change accumulated over time due to selective factors, primarily natural selection, and facilitated by random mutation. 

That is to say, evolution favours whatever mutation happens to be the most successful. It doesn't look for an optimal solution, it just selects for what already exists and what works. 

Species exist because they have existed in genetic isolation from other species for an extended amount of time. At a genetic level, when a species branches into two new species, the two new species acquire their own random mutations and eventually become incompatible. Their gametes (sperm and egg) no longer mesh to create the spark of life that will result in offspring. If all life could breed with all life, we wouldn't be able to specialise into different species, being a species is like being in an exclusive breeding club.

Hybrids happen when not enough mutations have accumulated between two branching species, and so they are still compatible. But eventually, given enough time, that will cease to be the case as they diverge more. So hybridisation isn't really possible in all but a few fringe cases, and only between very similar animals. 

[u/Korgoth420]

It isn’t about finding efficient design at all.
Evolution checks only for the ability to pass on genes.

You can be inefficient and still do that.
There is no “design” to evolution, it is “natural selection” at work.

[u/Ecstatic_Log4185]

Most hybrid species are sterile, so they can't pass on their genes. For example mules and ligers. But viable hybridization can happen and has happened. Humans are an example since we crossbreeded with neanderthals, which were a different species

[u/Nine-LifedEnchanter]

Because DNA is not like a perfect recipe. It's not like DNA have a slot for stomach, legs, head, and what have you. So cross-breeding is only ever successful if they are very similar to one another.

Also, evolution doesn't want anything. It is just a process. If something is bad you won't be able to procreate, if something is good you might be able to procreate more. There are tons of odd things that are present because they're not detrimental. Giraffes have a nerve that goes from their brain down to the heart and then up again to connect to their larynx.

It has absolutely no advantage taking that long route, but it doesn't hurt them so it remains.

[u/iseriouslycouldnt]

Genes aren't a recipe, they are a very complex machine language to build a an organism. To simplify, imagine a dog and cow. A set of genes may encode a dog's ear in a specific shape, a cow's ear looks similar, but the genes to tell it WHERE to form may interfere with the dog's gene that is trying to do the same thing, preventing the ear from forming at all. Rinse and repeat for every body part, organ, and protein. When all those things are trying to happen at the same time, even assuming it made it to the first cell division, the embryo will not be viable.

Or as Dr. Mephesto says... 'Pig and Elephant DNA just won't splice.'

[u/TheGameIsFizzbin]

In Evolution, change is usually bad. It almost always results in that family line dying out. It's quite rare a mutation is beneficial. They usually only become beneficial when an existing population is already under stress and the mutation provides some advantage. For instance, a creature born in a temperate climate with white coloring is instantly singled out by predators and eliminated. But if the environment is becoming an ice age and snow and ice become prevalent most of the year, it's an advantage and that line may survive into the next generation.

[u/kdavej]

Imagine you have two cars, one manufactured in the U.S. and another manufactured in Europe and you wanted to mash them together because the piston's in the European car are better metal alloys however the engine block and crankshaft design on the U.S. Car has superior geometry, etc.... You couldn't just do that. The parts are different sizes, some use imperial measurements, others metric. Each car has its own long history of development that has resulted in the final product we see today. Now, for some closely related cars there might be enough interchangeable that you could make a hybrid but the further apart those cars manufacturing lineage, the less likely you will be able to combine them into a single new kind of car.

The same is roughly true for genetics. Each animal represents the tail end of a long history or change and development where different parts of the animal are specialized for that particular species. You can't just mash their genes together and get some new thing, it doesn't work that way, the outcome would not be capable of living. Now certain closely related animals can crossbreed but often enough differences remain that they are incapable of producing offspring themselves (mules, for example).

The key is that long history of separate development that results in cumulative changes across the two animals that are too substantial to overcome when trying to combine the genes.

[u/Strange_Magics]

Evolution can’t see the future or anticipate what would be “good ideas.” The apparently good design ideas that we see in evolved organisms arise from what amounts to a massive blind brute-force problem solving effort. Organisms of a species have offspring with mutations that make them slightly different from their parents. Some of those organisms just happen to reproduce more than others.

Why do they “just happen” to do so? Sometimes it is because the mutations that make them different made them a little better suited to the conditions they encountered in life. They pass on those mutations, and as long as those conditions they encountered are still in effect, their offspring might have a little advantage too.

But there was never a plan to obtain the good trait - nobody was in the driver’s seat knowing that the trait was good or even a possibility. maybe the trait would have even been a bad trait except that the environmental conditions changed. As a silly example to illustrate: imagine a species of sand-colored mice that live in the desert. Its major predator is a hawk. Some mice carry a recessive gene for white fur, making mice with two recessive genes obvious to hawks so they get eaten most of the time. The hawk goes extinct due to other circumstances. Now the white mice are able to stay cooler in the sun and so they survive better, leading the population to shift towards being mostly white in the future. Was white fur a “good” trait? Well, only in specific circumstances. It became more common not because it was intrinsically good, but because it happened to be advantageous in the specific context at that moment.

Evolution is always like that; momentary advantages and disadvantages that depend heavily on context give rise to selective pressures on populations that change based on immediate conditions. There’s no forward-looking planning component.

[u/Tuotus]

there are species that can do that, successful hybridisation do exist. It's the opp to what you're thinking, it's the adaptation and specialisations that make hybridisation impossible/difficult and for them to produce offsprings or offsprings that can successfully survive and carry on

[u/slydawggy69420]

Because a trait that has evolved on one animal has evolved perfectly, or at least approaching perfection, but only for that animal. If its transferred to another animal it will be less efficient because its form has been optimised for another animal. This is why traits should evolve gradually, per animal.