Asterisk: sliding scale

The more pulp and other fruit matter in a juice, the less this is a problem. Clear juice is the worst - and in some cases, can be as bad as soda (especially if there is sugar added). Juice with pulp is better; and smoothies made from the entire fruit is only marginally worse than eating the fruit straight.

There's also an open question of some cephalopods like octopi. We know they're very intelligent; but we're not sure how to test if they are self-aware.

That's true if there is 100 fish - but not if there is 1 000 000 fish.

If there's a huge number of fish, the chance that a given gene is removed randomly is very low. Unless it provides a disadvantage, it's entirely random. There have been experiments, both in digital environments and in sealed live environments, tracking genetic drift (the change in gene representation in a population over time); and pretty consistently there are cases of genetic variations that end up spreading by chance that don't do anything.

The classic example of real-life variations are two different genes that code for the same amino acid chain using different base pairs - there's no advantage one way or another. In such a case, the most common result over time is that both versions of the gene persist; even if you start with one variation is less common than the other.

The exception is if you simulate bottlenecks - like the "100 fish" scenario you posted. With such small numbers getting through, it becomes a lot more likely for some genes to be lost forever by random chance - including useful genes that happen to get unlucky.

Except that while it's very hard to get it exactly right, it's really easy to get close.

Getting to 360ish days is relatively trivial - as best as we can tell, a 12-month, 360 (+- 10) day year was developed independently in at least India, China, Mesopotamia, and Mesoamerica - and that's a minimum: there's reason to believe that northern Europe, Mediterranean Europe and/or North Africa, Southeast Asia/Polynesia, South America, North America, and southern Africa also independently developed calendars that were not far off from 360 days. From a 360-day calendar, all you have to do is throw in a few non-year Holy Days before New Year (which, for many calendars, happens at one of the four main days - the solstices and equinoxes) until it's the right time, and move on. Alternatively, if your calendar is lunisolar, you add a month if New Year is too early.

Yes, getting things exact is really hard - even the Julian Calendar is off by a little bit, and technically the Gregorian Calendar is off by a little bit (it's off by .0003 days per year - or about one day in 3000 years). But I think you're selling human intelligence short saying it's not trivial to get a working calendar - as long as you understand the calendar isn't perfect, being a few days off isn't a problem. And both ancient calendars still in use (Chinese, Hebrew) understood that, and had rules to make sure that the calendar was not off by more than one month - and it's safe to assume they weren't the only ones like that.

It's worth noting here that the modern 365-day calendar is somewhat recent.

Many older cultures - notably, both the Jews and Chinese, who retain their older calendars - were what are called "Lunisolar" calendars. In these calendars, you have a set cycle of months, and introduce a leap month into the calendar if a specific month would happen before some yearly event. While I can't find that for the Chinese Calendar right now, the Hebrew calendar is normally 354 days, but adds a 13th leap month if the new year would start before the Spring Equinox.

Other people have already described how these people determined the solstices; and the equinoxes are pretty easy to figure out as well (halfway between the solstices - both in terms of time; and in terms of where the sun rises/sets).

You track populations.

For example, if there is a gene variation that you see in African Americans, but not in people in Africa, and is more common in African Americans than in Americans not of African descent, then it probably originated in the American South; and depending on how distributed around the US is it and how many people have the gene variation, you might be able to guess how old it is.

A notable real-world case is a specific mutation in the Y-chromosome found in about 8% of Asia stretching from northern China to eastern Europe. Because it's on the Y chromosome, it's (almost) entirely male-linked; and the working hypothesis is that the gene originated in Mongolia (it's more common there), and spread with Genghis Khan's conquests. The fact that this gene shows up more or less the same amount over such a wide area suggests that it showed up about the same time in all those places - and Genghis Khan explains that nicely.

They are more recent.

There were hundreds of units of distance a long time ago, when there wasn't a lot of communication or cooperation between nations - or sometimes even between cities in a nation (see: China, Rome). As humans spent more time interacting and cooperating, we standardized our measurements; but the US stubbornly refuses to change from the system it uses.

However, electricity was discovered and measured recently enough that competing units of measurement never got established enough for there to be significant argument over which units to use.

Here's a 200-page book, copy it by hand.

You may make a mistake.

That's DNA.

A virus's DNA is about 300 000 base pairs - which is about equivalent to a 200-page book. Granted, DNA has 4 characters while a book is written in closer to 64 - so maybe it's only a 65 page book; but you still have to copy it. Mistakes are going to happen.

Life generally takes two solutions to this: make a lot of copies as fast as you can and hope most of the books are still good; or take your time to make sure there are as few mistakes as possible.

THink of a ball. There's one point on the ball that's the top of the ball. It's a very precise point, but it's there. Any direction you go from that point isn't going around the ball - it's just down.

Once you're off that point, you can go around the ball. But on that one point, all you can go is down.

Earth is the same.

In more detail:

While some password hacks do go through the front end of the system; that usually doesn't work because of the account timeouts. Instead, most password hacks happen when a hacker gets hold of a website's password database. Given the database, a hacker can brute-force password guesses on their own computer without needing to deal with the front end.

Actually, literacy is actually a lot higher in historical England than the records indicate. This is because "literacy" was measured in Latin, not English; and as such there were a significant (likely over 25% of the population) number of "illiterate" people who could read and write English at the equivalent of a modern 8th-grade level.

Actually, we tricked rocks into thinking first. But the modern computer involves gas first.