I had to go back and reread Tender is the Flesh by Agustina Bazterrica to make sense of the ending. And here is what I make of it: Marcos never once looks at the “head” as anything human. Rather, it is the readers who still perceive the “heads” as humans. So all of Marcos’ actions, telegraphed through that lens, are seen as acts of compassion and love for a fellow human being. When it's not that at all. Marco never looks at the “head” as anything other than a pet, a fertile incubator for breeding, and a vessel for his child. In her, he finds some semblance of hope for a better future in which his child would be alive and well and fix the hole that his son’s death had left behind. All his yearning, longing, and concern is directed at the growing fetus in Jasmine’s stomach. He is always hugging her around the stomach or touching her stomach in some way whenever he shows any kind of intimacy towards her.
He also enjoys her company in the same ways he and his father once enjoyed the company of their dogs. He interacts with her as one might with an intelligent pet or cattle. He names her, teaches her the basics of survival so she can stay at home alone and not hurt herself (or his child) when he’s away; he teaches her to eat and drink, use the bathroom, lets her watch TV for amusement, feeds and clothes her, pets her head to reassure her. Marcos never teaches her how to be independent like a human who can survive beyond these four walls he keeps her tied to: he never teaches her to read as he thinks it's pointless “if she can't speak and will never be part of society that sees her only as an edible product.” It is a sentiment he also agrees with.
Marcos repeatedly says how, unlike his father, he never had any issues adapting to the “Transition”. As a post-transition man, he never has any problem differentiating between humans and “heads”. In fact, all of his actions towards Jasmine has a precursor, a knowledge bank of information regarding the care, breeding, and processing of FGPs that he draws from: whether it's the post rape cleanup of one of the FGPs where he learns the “heads” cannot talk but can be bread, or the discussion about their fertility (juxtaposed with his wife’s low egg count), or the description of how one of his colleague is able to sooth the “heads” by hugging them from the back and petting their heads, the consistent foreshadowing of the method of slaughter (hit the head with a blunt club before slitting the throat), or the cautionary tales of men falling in love with the heads and getting arrested for their crimes. Marcos carefully catalogues all of this information for when he finally sleeps with Jasmine. He even has violent, messy, raw sex with Spanel before he touches he brings himself to touch her.
The line “she has the human look of a domesticated animal" when he kills her in the end is likely because, done her part in birthing his child, the way she reacts, desperately reaching out to the child as he's being taken away. In that moment, he sees her as a domesticated pet whose grown human-like characteristics (still not quite seeing her as human). It's a direct comparison to his father’s attachment to the dogs and how he lost his mind when he had to put them down. But unlike his father, Marcos has no qualms about getting rid of Jasmine once she’s served her purpose. He never envisions a future with her even though he did entertain thoughts of running away from everything with her (while she was pregnant). Notice how he always refers to the child as “his child” or “his son” and finally “ours” when he holds the child up to his wife. He never once acknowledges Jasmine as the mother.
More than the dystopian nature of a world post-transition, it's Marcos’s actions that really drive home the horror of living in such an environment. Marcos is a fully post-transition human, completely assimilated to the divide in species between humans and “heads” as others. As horrific as it is, it's the only way of survival in a broken world where there is no room for morals and ethics. As for his lack of compassion, in a world this broken that might be a luxury for some. There are all kinds of suffering in the world, and not everyone has the capacity to feel empathy on a universal scale. Sometimes, personal tragedies can feel so all-encompassing that it selfishly trumps all other emotions. Marco’s personal grief over his ageing father, his eventual passing, the death of his son, and the dissolution of his own marriage means that he’s fully alienated himself from the larger society. His isolation and voluntary exile are a bubble where none of the horrors from his everyday life can touch him. He is desensitized to it all and fully subscribed to the “us” versus “them” mentality. Marcos never looks at Jasmine as human. He lacks the capacity to feel for her suffering. He takes care of her as a farmer tenderly takes care of his cattle, right before he cradles her body, and slits her throat for food to feed his family.
