I think that, in general, human babies and Pillar Men infants grow up more or less the same way. But in my opinion, the latter start understanding the world, walking, and talking much faster than a human infant.This is pretty much how I see Kars as a child — he's around 3–5 years old here.

His hair was probably a bit lighter than it is now, and his eyes were still round, though already showing some character. (Yeees... So tiny and already thinking about how to become the Ultimate Lifeform...) His horns at this age are still very small, without sharp tips. Also, this is the period when fangs actively form — the little ones are just exploring their bodies and are generally super curious. And his hair was tied into a little braid with a flower so it wouldn't get in his way (since it's really thick). Maybe his dad or mom did it. Later on, he just kept this warm childhood habit, and even as an adult, he continued to style his hair the exact same way.

Next up... Teenage years (13–16 years old)

During this period, teenage Pillar Men also go through a series of changes, specifically getting a pretty major growth spurt. Their horns become sharper and longer, and their facial features get more defined. In Kars' case, his eyes became more predatory and serious, his baby fat disappeared, and now he’s got cool cheekbones 😎🤘 Okay, maybe they aren’t quite as sharp as his adult ones yet, but they're already noticeable. Also, his fangs became much sharper. Their bodily abilities grow rapidly, and along with that, their appetite increases. Their bodies become tougher, despite the seemingly fragile look of a teenager. As they age, each of them noticeably gains muscle mass.

And finally... Adulthood (20–28 years old).

I believe that at around 28 years old, a Pillar Man's body kind of freezes in time. They no longer age or change in appearance. Since 28 is considered the prime age for humans (the peak of their physical form), for a Pillar Man, this is exactly that ideal body state that stays with them for 100k–200k+ years (or maybe even more). Meaning, if you were born a Pillar Man and reached 28, your body no longer changes. You can fight, start a family, live a long life, and not suffer from aging at all. However, despite their external eternal youth, they still age on a deep cellular level. The elders in the clan could be anywhere from 500,000 to 1,000,000 years old. Over time, the cells get tired, causing external fading and final death from old age.

I want to point out that Pillar Men probably still grow a little bit even after turning 20, but just like with humans, everyone's growth rate is different. What I really love is that in this race, both women and men are incredibly tall! Pillar Women can be about 195–210 cm tall, and Pillar Men — 205–220 cm. Yeah... For us, that would look like gigantism, but their body biology is just insane (literally!), so I think it’s totally possible. And it’s worth keeping in mind that they are all super fit and strong there. Long story short, they are the absolute top of the food chain.

But... There is something that bugs me to this day, namely: why is Wamuu 12,000 years old, while Santana is 10,000 at the time of Battle Tendency? After all, the flashbacks clearly showed that both Wamuu and Santana were infants! Did Wamuu really stay a baby for a whopping 2,000 years? I thought about this for a long time and came to the conclusion that this race probably knows how to put their infants into a state of hibernation (stasis). Back in those ancient times when their clan was still thriving, there were very few humans on the planet, and they weren't particularly nutritious either, so food was a huge problem. The Pillar Men had no choice but to turn their young into stone if there was simply nothing to feed them. But they could always bring the child back to a normal waking state as soon as good times came or the human population around them grew (what caring parents!). It turns out that Wamuu only started his full development after 2,000 years of such a stone sleep, while Santana grew up right away. Perhaps there weren't that many children in the clan in general, so Kars didn't even have to choose exactly who to save and train as future warriors . He just took the only remaining babies.

There is another theory about their sleep: I noticed that their sleep time is always 2,000 years for all of them. Perhaps for them, a 2,000-year hibernation is like 8 hours of sleep for us. Maybe that’s exactly how much time is needed to renew the cells in such powerful organisms.And I also noticed that Santana was angry when he woke up... It’s all because stupid humans kept him from sleeping his 2,000 years... I feel so sorry for him 🥺