But wait, if there's no objective morality, seeing as there's no objective basis for it, then how can you say that morality is predicated upon what is 'beneficial or detrimental to a species'? Do you mean that that's what you think morality is? That is, what you think morality is predicated upon?
It's easy to identify certain things objectively as being detrimental to our species. If the majority of us went out and indiscriminately killed complete strangers for absolutely no reason this is clearly detrimental. These people would kill the minority and then continue to kill each other, resulting in the end of our species or a population bottleneck so small that a simple virus might wipe out the rest of us.
Is this a problem for life on Earth in general? No! In fact it would probably benefit other forms of life greatly, but for humanity it is objectively detrimental - which is what people would call "Immoral".
If the you think that's what morality is then can you truly state that there's no objective morality and be consistent in saying so given that the 'beneficial/detrimental to a species' idea seems to be an objectively applicable basis for morality? Or do you mean that if people try to define precisely what the 'beneficial' and 'detrimental' mean, then it will result in different conceptions of the 'beneficial' and 'detrimental' and so, even this cannot serve as an objective basis of morality?
Covered at the end of my reply...
For example, upon this basis, we may decide that eugenics, social darwinism, and so forth, are good. We may think that it is entirely correct to euthanise and sterilise the disabled and lower-IQed in the interest of improving the race or lessening its suffering or potential suffering.
You seem to be classifying things as being either moral immoral. You really need to think of it as a sliding scale between moral and immoral.
Killing strangers sits highly toward the immoral end of the scale because
Benefit: zero
Cost: high
Having 100 million in the bank and giving away 1000 to pay for something to save someone's life is on the moral side of the scale because
Benefit: high
Cost: low
When you get into justifying the killing of thousands or millions of people the cost is very high, so even if the benefits are very high it will only get as far as being somewhere in the middle - neither moral or immoral. For it to be considered moral the benefits must be exceptionally high.
Ending lives is a great cost to our species. The more varied DNA that exists the more chance we have of surviving changes to our environment or surviving new diseases.
Surely this, however, is not in accordance with our understanding of morality? Of conceptions such as 'individual rights' which play such an important part in our approach to ethics? It seems that things are more sophisticated than judging what is moral merely by how something may harm or benefit the species collectively.
A specific right for an individual can cost very little and benefit the individual a lot.
Well, it depends on the particular characteristics of the objective morality involved. But say there existed the kind of morality that you outlined regarding the lack of moral opprobrium on a dog that forces itself onto another:
If the criteria you mention here, i.e., no harm to the female, good breeding partners, etc., are part of the basis of an objective morality then one may well apply this to an instance in which a male human forced himself onto a human female, but seemed to cause her no distress and ensured the reproduction of better genes. In doing so, we could, according to this understanding, maintain that it was not immoral for him to do so. So both could be considered perfectly moral according to one form of objective morality, the bases of which permitted such behaviour.
Physically strong breeding partners is no longer an issue with humans. We don't need the biggest + strongest male to fertilise eggs in order to improve infant mortality rates. Medical advancements are a far bigger contributing factor to lower infant mortality, and males no longer need to be the biggest and strongest in order to provide food and shelter.
So there is no benefit in a human forcing himself on a woman, and a high probability of there being a cost to the woman such as emotional distress and even physical damage which can lead to infertility.
You are asking if rape would be moral if it had benefits and no costs, the answer is "yes, just as it is in dogs" but the reality is that our species are very different from dogs. In dogs I would not call it rape, I would call it "their breeding process". In humans there are high costs and no benefits which is why it is detrimental and why it is therefore classified as immoral.
But it really just depends on the criteria you use. Going with a utilitarian ethical approach we may say that it's immoral for a human male to force himself onto a human female because that female would suffer considerably as a result, whereas it's not immoral for dogs to do so because the dog itself does not suffer as a result. You see, the matter of the suffering of the subject is being used as the basis of determining what is right and wrong in such cases. It is the hypothetical objective standard in such cases and yet the two actions are not regarding as being morally equal.
There is a reason I used the example of killing complete strangers without reason. There is no question at all that to our species it would be very detrimental if everyone went out doing this. This shows that you can objectively say that something is detrimental to our species and therefore to objectively label it is immoral.
Unless, of course, you mean an objective morality that is entirely different from anything else we know about or can think of, in which case, you may be right that according to that objective morality both actions would be wrong.
My argument isn't about how to decide how far up/down the moral..immoral scale something should be placed, but to show that even if you feel you can identify something as being immoral using objective rationale it does not prove there is such a thing as objective morality. There are things which animals do which are beneficial to their species which would not be beneficial to the human species, and forcing our species' behaviours on another species might be detrimental to that species too.
If there were such a thing as objective morality then the same things would be moral for animals as are for humans.
If one wants to argue that there is objective morality for humans only then one also has to explain why animals display signs of having many of the same apparently moral behaviours.
If one wants to argue that there is objective morality which changes depending on the species then you are accepting that this "objective" morality is subject to circumstances (i.e. which species you happen to be) in which case it is subjective morality.
Topic: Objective morality