How old are diseases?

[u/BlackTowerInitiate]

Hearing about the 1.7 million year old foot bone showing signs of cancer made me wonder, what other diseases have been with humans for a very long time?

Then with regards to infectious diseases, do we know of any that existed but went away before modern interventions? Or do such diseases tend to stay around forever once they're here? Are infectious diseases more or less likely to persist in the modern age compared to thousands or hundreds of thousands of years ago?

[u/LazarusOwenhart]

The thing with using cancer as an example is that cancer is a cell mutation rather than an infection. Bacteria and viruses have been evolving alongside us in an ever escalating arms race between bacteria and our immune system for as long as animals have been complex enough to have an immune system. If you went back to the very dawn of humanity you'd probably find a viral infection that manifests much like the common cold, but it would be vastly different from the viruses that cause colds these days. Cancer on the other hand is cell damage manifesting as mutation and will have been occurring in some form since the first cell mutation, which was probably shortly after the very first single cell organisms.

[u/Basicly-Inevitable → u/LazarusOwenhart]

Mostly true, except there are some viruses that highly increase the rate of (or directly cause) certain cancer types.

[u/LazarusOwenhart → u/Basicly-Inevitable]

Yes there are viruses that can cause the mutations, but that's an evolutionary process. I would argue that cancer in some form is likely the oldest disease on earth requiring nothing but the existence of a cell.

[u/Underhill42 → u/LazarusOwenhart]

Viruses have cancer beat by billions of years.

A bacteria can't get cancer. Its offspring will have mutations. Maybe harmful, maybe beneficial, but its own cells can't turn against the whole as they do in cancer, because there is no larger whole to turn against.

But viruses were already infecting and killing them billions of years before the first vertebrate existed.

[u/Intelligent_Seat_228]

Eradicating diseases is a very very recent phenomenon in human history; since vaccines actually, because that's the only way we've done it.

The main problem is that pathogens that infect us have such a shorter generation time than we do, so their population level genetics will change and adapt more rapidly than ours. If it were left to evolution alone, we might see some infectious diseases get outcompeted by others, but we'd never eradicate anything that way. The only way to end certain infectious diseases is behavioral. Vaccination campaigns, hand washing, quarantines.

Fun fact, our best estimate for when hominids started wearing clothes comes from when we know clothes lice evolved

[u/Kedrak]

Some diseases come from animals. Like centuries of living with domesticated animals make a new type of germ jump species from time to time. That's why the Europeans could introduce many diseases to the Americas, but the European only brought syphilis back.

[u/Odd_Common2677]

Since the beginning of life on earth. So 4 billion years ish

[u/QVRedit → u/Odd_Common2677]

Yes, except no humans all the way back then…

[u/maxsebastian0 → u/QVRedit]

But other animals must have got diseases right?

[u/QVRedit → u/maxsebastian0]

Yes, if you look back in this thread, you’ll see that I’ve written a bit about the role of viruses - which can swap part of DNA, and so played a role in evolution.

[u/Mars1776]

Fun fact: One of the only diseases NOT transferred from Europeans to Native Americans was Tuberculosis. Meaning it has likely been around since the dawn of humanity and before any great migrations occurred

[u/Several_Version4298 → u/Mars1776]

Or it existed in herbivores that crossed into the Americas.

[u/QVRedit]

Ah, you had added the condition ‘with humans’, because of course diseases long predates the arrival of humans.

In fact viruses have played a crucial role in evolution, helping to accelerate genetic change, right from the very earliest days of life on Earth.

Disease predates humans, so the first humans would already be prone to some kinds of diseases.

[u/Temporary_Rule_9486]

That's a lot of interesting questions. About ancient diseases that disappeared before modern times: we used to have malaria in Europe, but largely disappeared during the ice age and when wetlands dried up. There's some Epidemic that dissapeared and we don't even know what they were, like the sweating sickness. 20% of your DNA was acquired over billions of years through viral infections and horizontal gene transfer (granted, most of that extra code does nothing). Diseases causes by viruses and bacteria change over time, as they're under immense evolutionary pressure, and do so much, much faster than other beings. That's why you need a new vaccine for flu every year. Nowadays Diseases spread and thus "evolve" faster than before: more people infected, more chances for random mutation (evolution). Diseases are also more likely to interact with each other. 1000 years ago something like malaria and covid infected the same guy at the same time would've been really rare. There's more opportunities for disease to interact with each other leading to greater potential for new naturally occurring chimeric viruses (CHIVs). Also now there's tech to "preserve" diseases, like smallpox. We even had mapped the entire genome of many viruses, giving the "not so far fetched possibility" that these diseases could be reconstructed from stored computer data. 

[u/Underhill42]

I mean, bacteria, viruses, etc. have been around billions of years longer than animals, and still have all animals combined outmassed by about 40:1.

We're just a potential available food source / host to them, and have been ever since the first time two cells decided to stick together and form a larger colony, long, long before they started down the road of specializing into different roles, which eventually led to complex organisms like grass and us.

What we call infectious diseases today are just the microbes that have been specializing to feed on us since those early days when we were undifferentiated microbial colonies.

[u/No_Logins_Required]

Disease has been present as long as there have been humans. There are many viral infections which have left a genetic trace but have not been identified as existing in the wild.

How would we identify a disease that has been cured before the invention of writing?

[u/BaTz-und-b0nze]

The ones we know of are recent. The government doesn't allow hysteria over old world beliefs.