@futurebird Unusual combinations of metals in the bones. Greater concentrations of heavy metals and petrochemicals than expected for 21st C humans in time travellers from the future, lower concentrations in those from the past.

@futurebird Individuals who lived between 1945 and about now have greater carbon-14 levels in their bodies (from the atmospheric nuclear detonations from 1945 to 1963) than anyone who lived before.

But unless more nuclear bombs get detonated, new babies born will soon have no more in them than people who died before 1945.

@futurebird

I assume you already know about the Baby Tooth Survey: https://en.wikipedia.org/wiki/Baby_Tooth_Survey .

@michael_w_busch

I did not!

@futurebird Chemicals based on diet? Size of person (good nutrition, bigger). We also absorb what’s in the air and water.

How do we know what they ate?

The foods eaten by our ancestors can tell us a lot about their lifestyles and the environments in which they lived. Food has also played a major role in human evolution, particularly when meat became a significant part of the human diet about two million years ago.

The Australian Museum (australian.museum)

Carbon dating: https://www.futurelearn.com/info/courses/skeletal-analysis/0/steps/59520

@futurebird

Apparently; showing JFK baby teeth laced with strontium-90 was persuasive in getting the test ban treaties through.

@CStamp

The bones carbon date to 4k years ago, but the dental work is modern. The plaque contains DNA from variants of crops no longer commonly grown.

The reconstructive surgery on the knee is made of 3D printed bone, beautiful work, someday we might do something like that.

@futurebird they probably just hum constantly at a very low frequency

@futurebird their immune system might look quite interesting indeed.

@futurebird depends how much shrimp is in their diet

@catmisgivings

Why shrimp? Did people eat more once?

@futurebird @CStamp There was a scene at the end of the 1968 Planet of the Apes, not involving chemical analysis, where they looked at an artificial heart valve in a human grave as evidence of an ancient human technological civilization.

@futurebird @catmisgivings

That seems unlikely given how much shrimp we eat today. It's a lot.

@futurebird oh I was just imagining that cesium-137 continues turning up in shrimp
https://www.nytimes.com/2025/08/20/business/radioactive-shrimp-walmart-recall.html?unlocked_article_code=1.FFA.CwHN.m87yL68TGK2o&smid=nytcore-android-share

@futurebird@sauropods.win Certain types of surgery and dentistry would be pretty obvious, but not for everyone.

Maybe some kinds of microbes that persist after death? If the species on the skeleton are significantly different from other skeletons from that time, it'd be suspicious. Probably not a smoking gun, though.

@karabaic @futurebird @CStamp The point of that scene was to show that humans were weak and fragile, if I remember correctly.

@futurebird @CStamp

There are bands across my teeth showing when I started drinking fluoridated water.

But that wouldn't tell someone in the late 1800s if someone was a time traveler or if they simply grew up in Colorado.

@bruce @futurebird I wish I remembered the figure for what proportion of the Lenape diet was fish and seafood at the time the settlers came, but I was astonished. A third? Half? The catch was ridiculously abundant

And these guys who came over from England wanted MEAT and perceived that they were gonna starve on Lenape land

@futurebird If someone had been born after a nuclear war, that would show up in their teeth and bones in terms of much higher levels of radioactive strontium compared to contemporary humans.

@futurebird Fluorine in the teeth; dental work generally. (Orthodontics leave traces! Implants on titanium posts rather more so.)

The other thing is that this kind of thing is generally very coarse; "its diet was C4 plants" has been the result for jaguar skeletal remains. (They were ritual jaguars fed on corn-fed turkeys, far as anyone can tell.) Absolute proof of time travel would take something impossible at tech level like that titanium post.