In my world, all of my demihumans have evolved from the same ancestor from modern humans. This conceptually includes my version of Reptilians/Lizardfolk. For the most part I would have them share the same anatomy as regular humans. But they're called lizardmen for a reason. So, if possible, I'd have them have these traits:

  • Scales, which can cover most the amount of the body. Maybe some can have patterns and make them have camouflage?
  • Long tails that could regenerate.
  • Eyes that have color vision and more advanced visual depth perception.
  • Claws on their hands, which can be used for tool-making, and reptile-like feet.
  • Some may develop venom in their mouth to use as protection.

With all of these attributes in mind, how could they evolve to become the reptillian-ish humanoids I have in mind?

  • $\begingroup$ "Some may develop venom in their mouth to use as protection" You might want to check out my old question Could venoms evolve naturally in mammals? $\endgroup$
    – user
    May 26 '18 at 19:44
  • $\begingroup$ How far back on the evolutionary tree did your guys break off? This question is insanely broad because as it stands, this split could have happened anywhere. You say the same ancestor as modern humans, but which one? Homo erectus? Homo habilis? Or somewhere further back than those even? $\endgroup$
    – Pleiades
    May 26 '18 at 20:15
  • $\begingroup$ There is a popular opinion that opposable thumbs are important in developing real human-like intelligence. Sometimes it's presented as the thing that made us what we are. Several dinosaurs and according to wikipedia even most birds have them which are of course related. I think the question "how could x evolve" is based on a complete misconception on how evolution works, it kind of implies something like a cosmic plan, and is not answerable, but if you want to know how to present it in a story, base them on a reptilian with opposable thumbs. $\endgroup$
    – Raditz_35
    May 26 '18 at 21:56

Within a few million years, some of these characteristics are possible.

Claws: The lizard men evolved in a dry rocky area with scarce water and wood, but lots of caves, canyons and cliffs. To help climb and dig for food and water, their fingernails got long and thick. Almost claw like. As time went on, the wealthy tried to grow longer claws to differentiate themselves from the lower classes who had blunt nails from working. So warriors and the well off have claws either real or fake metal ones, while the rest have thick dull fingernails that are still quite formidable.

Scales: From the hot sun and rough terrain, the lizard men developed thick skin. This skin looks scaly, as it has a pebbled texture, but it sweats and is simply a thicker version of skin.

It's similar in colour to the rocks of their homeland. Some families or clans have tried to breed certain colours into their skin, with varying degrees of success. Inbreeding is a problem for the most insular clans that emphasize colours, so it's not common.

Eyes: Easy enough. It's a beneficial mutation that happened early on.

Venom: Like a monarch butterfly caterpillar, some of the lizard men living in harshest parts of the desert eat poisonous plants to survive. They've developed the ability to survive the poison, whereas even other lizard men would die or suffer severe illness. The ones who eat it throughout childhood have the poison build up in their system, particularly their saliva glands, but also their tears and kidneys. If they bite someone, vomit on them or spit in their eyes or mouth, it can cause the person to feel mildly ill in a few minutes. If they save their spit, tears or urine and specially prepare it, they can make a poison that is much stronger.

This has the unwelcome side affect of making those who aren't immune to the poison sick if they french kiss the lizard man or have sex with them.

Tail: Sorry this isn't really possible, especially not having it able to regrow. A tail is just not beneficial to how we walk.

  • 2
    $\begingroup$ With regards to the tail, humans managed to develop a way to keep our balance without one. Humans are a blatant exception to the normal rule in that regard; having a tail would actually make it easier for us to maintain our footing, not harder (assuming our bodies were accustomed to a tail, as opposed to one spontaneously appearing by magic). You don't tend to notice it, but humans can't really stand perfectly still: there's always a little movement in the legs and feet, small adjustments to maintain balance, since a bipedal stance is unstable in the absence of a counterweight (like a tail). $\endgroup$
    – Palarran
    May 27 '18 at 5:19
  • 1
    $\begingroup$ @Palarran, our large butt cheeks already act as a tail, adding another tail, especially a thick lizard like one would be a waste of resources. More importantly the last time a human ancestor had a tail was about 20 million years ago, when tailless great apes split off from monkeys. Those tails were long and thin, mostly for grasping and balancing in trees, very different from most lizard tails. I just can't find a reason for a lizard like tail to develop in an evolutionary short amount of time. $\endgroup$
    – Dan Clarke
    May 27 '18 at 5:40

There is no scientific way this could happen. Animals sometimes evolve analogous structures for a specific purpose (like the wings of a butterfly, a bird, and a bat, or the scales on a snake and a pengolin). However, the chances of animals from distinct evolutionary lines simultaneously evolving all of the features you describe are basically nil.

For a homonid, developing claws is a disadvantage. You can't use tools as well. A tail is a disadvantage, it prevents you from walking upright. Scales and venom require extra energy, and what use do they serve for a homonid that has no predators because it lives in a social group that can defend against any predator?

  • 1
    $\begingroup$ I don't see how a tail would prevent someone from walking upright. In many mammals, it's a tool to maintain balance; humans are the only known bipedal creatures without tails, and it's actually quite remarkable that we don't constantly fall flat on our faces. There might be other reasons why a tail would be disadvantageous, but that is most certainly not a reason. $\endgroup$
    – Palarran
    May 27 '18 at 5:13

For scales, atmospheric pressure could be a driving factor. Bigger and stronger predators for the camouflaging

Tails could be a biproduct of a need for a strong upper body build. They would need to balance their body if they are bipedal and walk upright. The regenaration can be the same as modern lizards. The need for a tasty bait for these vile predators while they run away.

For eyes to be able to see vibrant colors, the environment need to be colorful and vast. Maybe a forest with many poisonous stuff, which has different colors as warnings. They may also have a need for scouting from a high position, for navigating and for surveillance.

The claws can come from a need to climb trees to scout surroundings or flee from predators, or self defense.

The venom can be a byproduct of choosing which foods are mildly poisonous, but still choosing to eat them because they are non-lethal. The poison would gradually accumulate to lethal amounts in their mouth. Or they can be from the absence of dental hygiene, like that of komodo dragons. The bits of food that remained inside their mouth would rot and bacteria would develop there to lethal amounts. Their breath would also smell terrible.


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