How far back in time can we go before people start to look different physically?

In other words, assume we have a naked man and women in an anthropological police line up. How up how far back in time can we go before that man and woman start to look marked different than modern humans to the point we could readily distinguish them as “something else”?

I am pretty certain we did this exact question recently. I will see if I can find it. It is a difficult question because acceptable answers can range from not that many thousands of years ago to millions of years ago depending on the type of answer that you want.

You mean the ancestors of living humans today? You’d have to go back >200,000 years, since that’s about the time that we say physically modern humans appeared on the scene. But you can drag in a member of any of these species from 50k years ago, and they’d look **very **different:

Homo neanderthalensis [extinct about 28,000 years ago]
Homo erectus [extinct about 30-50,000 years ago]
Homo floresiensis [extinct about 12,000 years ago]

In case it wasn’t clear, those other species co-existed with Homo sapiens for quite some time, but are not considered to be our direct ancestors. For the vast majority of our history (since we split off from the chimp line) there has been more than one upright walking hominid species on the earth. It’s only very recently that there has been only one species-- us.

Since evolution is a very slow process that does not move in a straight line, it is difficult to say. I would compare it to the tree growing in my backyard. I brought it here on the back of my car some 25 years ago. It fit quite easiily in the back seat. Did not even touch the car roof. It is now about 9 metres tall (like a three-storey building). Every now and then a see a picture of the yard from 5, 10 or 20 years ago and I can see a definite difference, of course. But from day to day, or eben week to week, absolutely not.

Then again, you could not just compare one or two humans from today with one or two humans from, say, 50,000 years ago. I mean, just look at the variation in living humans today. Short, tall, fair, dark, etc. You would really have to examine a huge, representative sample of people from the present and 50,000 years ago. And I don’t know how you would do the latter.

On tghe other hand, I doubt if an Australopithecene like Lucy, whose remains date back millions of years, could “pass” in a crowd of modern humans.

So I guess the only anmswe we can give with certainty is: The longer the gap, the more likely you are to notice differences.

It’s unlikely that our ancestorsof 50k years ago had anywhere near the physical diversity we see today. In fact, there probably were only a few thousand of them back then. We really don’t start to see the modern racial differences in the fossil record until about 10,000 years ago (judging from only the bones, of course).

twenty-five years. My wife looks nothing like she did then. But then she says the same of me.

Actually, as I think about it, the physical diversity we see today would make an ancient human blend in more easily. Our skin is every shade from deep black to pale white, so unless they had green skin, they’d be somewhere inbetween. We have very short people and very tall people-- so unless they were 4’ tall or 8’ tall, they wouldn’t look that odd.

The lower part of our bodies (neck down) haven’t changed much in 2M years. We’ve become more gracile, but that’s not something we’d necessarily pick out in in a poice line-up. It’s the head that really looks different. The defining characteristic of Homo sapiens (aside from our teeth) is the flat face, vertical forehead, reduced brow ridges, domed cranium, and rounded back of the skull. Some of the limb proportions are slightly different in the Neanderthals, but they probably wouldn’t be too noticeable to the casual observer.

An Australopithecine, otoh, had longer arms and a chest more like a chimp-- narrow at the top and wide at the bottom. And of course the head looked even more chimp-like than our immediate ancestors, athough you wouldn’t see the prominant canine teeth of a chimp when he openned his mouth.

It doesn’t appear to take long to see minor variations. I remember watching a Japanese documentary comparing people’s jaw lines from pre world war 1 with today and there was marked difference, apparently from the change in diet. The modern diet needs less chewing so jaws have shrunk. Also, Japanese legs are getting longer because people are using chairs instead of sitting on the floor.

That sounds like very flimsy evidence to me, especially about leg length. Japanese today are taller because of improved diet.

Oh yeah, I forgot one other feature of H. sapiens– the chin. You don’t see pronounced chins in pre-sapiens populations.

This kind of thnking sounds to me very close to Lamarcksim, which is scientifically discredited and forms no part of modern evolutionary or genetic theory. The only way that this observation could comform to current evolutionary thinking would be if you were suggesting that the jaw modification somehow affected fitness for survival.

As to the OP, I don’t think I can improve on Valteron’s answer: the further back you go, the more apparent the difference.

Also depends on how you choose your subjects. If you pick out a random American man and woman from a few generations ago, there’s a good chance they’re European in appearance. The chances of that are a lot less now. In a few more generations, it will be even less likely.

That’s evolution in action.

With me, you only have to go back to about 3 AM.

I don’t think MelCthefirst was suggesting this – simply that in an individual’s lifetime the differences in lifestyle affect how that person develops. Less chewing means less muscle definition on the jawline, etc. Seems plausible to me, and no Lamarckian evolution is needed.

Thanks - yes, that’s what the programme was saying (not me, I add).