I recently read Robert J. Sawyer's Hominids, the first book in a trilogy about a quantum portal that opens between our world and a parallel universe in which humans went extinct and Neanderthals developed into an advanced technological culture. I enjoyed the first book, despite some glaring implausibilities, a bit of preachiness, and a distracting subplot involving a character being raped. And then I went on to start the next book in the series, Humans. But I only made it about halfway through before abandoning it. I really don't like giving up on books, especially ones that I've invested a fair amount of time in, but I just couldn't go on.
The flaws of the first book were accentuated in the second. In Hominids we find out that the Neanderthals never developed agriculture, and yet they found cities and develop advanced technology, such as AI implants called "companions" that assist them and record everything that happens around them. But how could a hunter-gatherer culture have the stability to settle down permanently and engage in the sort of division of labor necessary to advance technologically? Humans has an extended discussion of this, in an exchange with a Native American anthropologist, who manages to point out the arrogance and stupidity of "white people" while pointing out that it's perfectly plausible. The explanation rests on such a culture not growing beyond its available food supply by excessive breeding, and by not overexploiting their resources.
The Neanderthal visiting our world seems astonished that we would ever hunt another species to extinction. He also seems astonished that we would breed as much as we do. In our world there are over 6 billion people; in his world there are only a couple hundred million Neanderthals. I guess while they were developing advanced AI and physics, they didn't learn dick about ecology. No one should ever be surprised when a species exploits resources to the greatest extent possible and maximizes its reproductive potential. Evolution is a greedy algorithm. Individuals seek to maximize short-term gains; there is no foresight in evolution. A co-evolving population of predator and prey or bacterial infection and host population will typically oscillate. Fox populations increase as they prey on rabbits, but as the number of rabbits decreases, they are scarcer, so the fox population declines, which in turn allows the rabbit population to expand, and so on. If the foxes overexploit the rabbits and drive them to extinction, then the fox population will probably die out if that was their main source of food. What keeps this from happening is the reduction of the number of rabbits, not foresight by foxes, either individually or collectively. The foxes don't keep themselves from driving the rabbits to extinction. They do what they do. They hunt, eat, and reproduce as much as resources allow. This idea should not be surprising or shocking to a scientist.
We also get chided for polluting the environment (Neanderthals have sensitive noses, so all their locomotion is environmentally safe). They have no crime (because they have an Orwellian monitoring system and practice eugenics). However, the darker implications of the Neanderthal society are not really explored. Instead, human society is constantly portrayed as stupid and short-sighted.
However, it was Sawyer's ham-handed handling of a human character's rape that put the nail in the coffin for me. Being a geneticist, she collected the DNA from her rape instead of going to a hospital or the police. But the DNA samples are lost and she gets upset. Another woman in the area is raped, and this character blames herself for what happened. The Neanderthal tells her she needs to forgive herself, and so we get a scene where she goes to Catholic church and goes to confession. And that was enough for me. The rape subplot already seemed mildly exploitative, but its featured prominence in the second book and its awkward handling just drove me away from the story.
Which is a shame, because Sawyer's prose is incredibly crisp and readable. There are a lot of interesting ideas to explore in such a setup, but Sawyer instead writes a talky, polemical diatribe that's thin on story and stretches willing suspension of disbelief to the snapping point.