In the post titled Can Atheists Be Moral? That’s the Wrong Question , shared by +Andrew honest , the author of the article makes the excellent point that atheists can and do behave morally, even according to theistic standards. Atheists I know are often very honest and sincere even to a fault. Of course, I don't want to generalise, maybe I have been lucky with my sampling.
With that aside, the post goes on to address relativism, cultural differences, genetics and instinct as the sources of moral behaviour. I can't speak for relativism, as I am not one (despite apologists' repeated assistance that all atheists are), but the natural case for morality is not adequately understood by the writer of the post to even be relevant to making a case against morality as a natural phenomenon.
In the section titled "Morality is Not Genetic", the author states:
"If we truly believed that we merely “dance to our DNA” as Richard Dawkins stated, we would have no reason (or grounds) to tell someone that what they have done is wrong or inappropriate."
The author does not go through the trouble to learn about the case that morality as an evolutionary trait states at all. It does not state that genes are deterministic with absolutely no flexibility in our behaviour. This is an easy misunderstanding to make. Genes don't program how our brains will respond to every single situation and stimulus, it merely puts in place the structures necessary to function in a general purpose kind of way. So instead of a set of moral rules being coded directly into our brains via our DNA, there are simply emotional and logical "programs" that take in information and make decisions based on available information. The idea that genes are fully deterministic and that people can't help themselves due to genetics is simplistic and mistaken.
The author goes on in the section titled "Morality is Not Mere Instinct":
"Similarly, it cannot be shown that morality developed over time as a means of self or group preservation. If this were true, doing what was in our own best interest, or the interest of our “tribe,” would by default be the right thing to do."
And it is. If we look at morality from an anthropological perspective, we see that attitude pervading many cultures. In fact the author at +Reasonable Theology should ask himself why it is that people are starving and being murdered in some places of the world, but when a single white child is abducted in the west the media goes into a frenzy. This indifference to outsiders is explained by morality as a natural phenomenon, but not as a god given sense.
The author goes on:
"Even if it helps us get ahead, we still understand that cheating is not the right thing to do."
Any evolutionary psychologist will tell you that detecting cheaters in a social context is of utmost importance. The reason why organisms in social contexts don't just cheat the whole time is because when everyone else finds out that someone is cheating, the cheater is punished. To avoid punishment, we have to some extent evolved a sense of fairness and integrity. This emotional equipment encourages us to avoid cheating, even though many of us still feel okay doing it when nobody is looking and the risk of punishment is gone or diminished.
"The very definition of altruism is “the belief in or practice of disinterested and selfless concern for the well-being of others.” If morality was the result of some herd mentality, altruism could still exist. However, it would be deemed a weakness and not admired."
Why wouldn't an organism admire another organism that does things for it without expecting anything in return? Speaking in evolutionary terms it would be stupid not to admire altruism in others. It can indeed be a weakness if an organism gives away too much, unless it gives away to its offspring or family members, thus preserving the genetic material of the group even though it sacrifices its own life. Many animals die shortly after reproducing, because evolution doesn't select for any traits that prolong life unless a prolonged life is directly responsible for more successful offspring.
A single member of the group can sometimes seem to be highly self sacrificial. It is then almost definitely the case that the organism is closely related to the others that they sacrifice themselves for. What seems like an act of pure altruism is actually just a group survival strategy. The overall genetic identity of the individual is preserved, even though it loses its life, because its family members are genetically close to itself.
Human beings and many other social species operate on a principle known as reciprocal altruism which works a bit differently to pure altruism. The idea is pretty simply to give first as a sign of good will, and then something will come in return. A great example of this principle is the lover's quest. The lover will buy the object of their affection gifts, sing songs, make lofty gestures and pay extravagant compliments. A lover, blinded by a chemical soup that could well be the best drug known to mankind, will give these things selflessly. However if the receiver of these gifts does not eventually reciprocate the giver becomes jaded and feels cheated, even though they gave freely with no expectation of receiving anything in return. In a mutually loving relationship the giving, compliments and favours carry on, and a powerful pair bond is forged.
The concept is simple: give to receive. We engage in this behaviour with gift giving too. It is an integral part of human social order.
All these innate properties and behaviours don't carry us to a modern moral system, it just gives us the tools we need to get there. We co-opt familial love into larger entities like countries when we refer to the father land or to all humanity when we refer to mother earth, implying that we are all family. That means that instead of not being nepotistic as our nature makes us, we just convince ourselves that our family extends over the entire earth. In fact that is one of the most beautiful aspects of evolution, the message that we are all family.We take the tools we have in our minds and reason collectively to build ever better moral systems, starting from tribal dictatorships to democratic nation states.
These concepts are not simplistic. They do not occupy singular paragraphs, but span across multiple fields of study. If the author of this apologetics article wants to object to naturalistic morality, I think it would be fair for them to become aware of these facts and the study that surrounds them. As usual, the natural explanation does not only consist of real tangible science and facts about ourselves, but it presents a reality that is far more interesting than a "universal moral law" and a "universal moral law giver".