That is an excellent question. Thank you for raising it. I would like to respond against the philosophical framework of cultural evolution, investigating myths as memes. So the first point is to ask, who does the selecting?
In genetic evolution, nature selects. That is the meaning of the concept of natural selection. Genes that are best adapted to their niche prove to be the most durable, stable and fecund, and are selected to reproduce.
The same, or very similar, causal process applies with the memetic selection of culture, including Gods. So, the societies where warrior gods have been selected have by definition lived in places and times where those gods were the most adaptive. Warrior gods came into conflict with gods of peace and defeated them. That conflict is the main theme of the first of the real ten commandments in Exodus 34 – smash the groves of the goddess worshippers.
My view on why violent gods proved adaptive in the iron age (1000BC-0) connects to precession of the equinox, as the main physical driver of long term natural climate change. The 21,000 year climate cycle driven by precession was in fall during the period that the Bible identifies as the fall from grace, from about 4000 BC to 1000 AD, as shown from this orbital diagram
. This 5000 year period of precessional fall is defined by the date the perihelion moved through fall, until it reached the December solstice in 1246 AD. This fall period saw the rise of metal and agriculture, with progress in technology providing material abundance to pay for priests and soldiers. The emergence of settled wealth generated conflict, and the gods who were best able to protect societies from war.
In this context, religion acquired a military purpose, unifying society for security and defence. In Israel, a small country surrounded by big empires, the evolving religion of monotheist patriarchal hierarchy wiped out the previous diversity in order to build conformity for defence. The violent volcano storm God Jehovah proved the most adaptive support for national unity.
My view is that the previous love of war gods was due to their adaptive value. The social importance of war meant that martial values were prized, including love of drama, conflict, violence, horror, domination, etc. However, now that the world has globalised, this adaptivity of war is gradually becoming redundant and obsolete. It is highly noteworthy that Jesus Christ was a god of peace and love, but was crucified for his troubles, indicating as Isaiah foretold that the world would despise and reject the man of sorrows. That applies equally to a fictional and to a real Jesus.
The Gospel story, in Matthew 24, says the message of the kingdom will be preached to the whole inhabited earth and then the end will come. My view is that the Gnostic authors of the New Testament could see that the world was not yet ready for their message of peace and love, but that this message could grow within the womb of the old war god values, as dogmatic belief, until humanity is ready for a paradigm shift from war to peace as the basis of security. The security paradigm is also linked to a cultural paradigm shift from belief to knowledge as the primary social organising principle.
Your comment “our instincts force us to seek the fittest” is unclear. The evolutionary concept ‘fit’ just means ‘adaptive’, not strong or healthy. We should hope that our instincts do drive us toward greater evolutionary fitness, but this is not the case, given the instinctive basis of maladaptive traits such as obesity and sloth.
To be fit we must struggle against instinct. Christianity fits in this struggle in an interesting way, with its core message of love for enemies. The Gospel indicates that the mentality of war is a path of destruction, and humanity needs to identify and shift to a new paradigm to avoid destruction, which in modern terms means social collapse and potentially even human extinction as a species.
The destruction of local matrifocal belief systems was a gradual process, overall linked to the shift from stone to metal as primary technologies. The scale of society that metal enables involves a hierarchical organisation that can readily squash any local independent culture.
Again, the concept of ‘fittest’ has to be distinguished from what people believe. When people are deluded, their belief is by definition unfit in the long term, even though their delusion can deliver short term immediate advantage. The reason for this is that by definition, adaptivity means in accord with the natural context. A delusion is a false belief, so cannot align with the real natural context, even if it seems to align successfully to prevailing opinion.
The binary metaphysics of ‘women good, men bad’ is far too simplistic. Women also benefited, at least in economic terms, from patriarchal martial culture, even though at the cost of their social power and equality. Many women have been staunch defenders of patriarchal religion.
Idealising the stone age has its problems, as Steven Pinker has documented in his book The Better Angels of our Nature
, on the decline of violence. I personally agree with your implication that stone age life had far higher quality than imagined in common stereotypes. For example it is likely that small autonomous communities were better able to maintain gender equality, and had better happiness and work-life balance than modern societies.
The Yahwist war god was adaptive for Old Testament times. The problem is the effort to continue this model among Christians, even though Jesus insisted in the Sermon on the Mount that the old covenant of revenge had to be replaced by a new covenant of love.