My good friend Jeff Mann, the true Yard Ramp Guy, has asked me to revisit some of my original posts. This week in my From the Archives series: what's that archaeology team doing in my kitchen?

My watchdog never needs walking.

We usually think of fossils in the context of museums, but you might be surprised to hear that they're probably in your home without you knowing.

The first way this happens is pretty obvious: if you've got limestone as part of the construction of your house. Limestone is almost universally fossil-bearing. In fact, many types of limestone are almost entirely made up of fossils. So, if you have limestone in your house, you've probably got fossils.

Of course, fossils can be found in other rocks as well, such as certain sandstones and mudstones, though limestone is the most common fossil-bearing rock used in construction.

Next is in kitty litter. Bentonite clays are used in countless industrial settings, but they also have one extremely common use inside the home—as the main ingredient of most kitty litter products. Bentonite clay is highly absorbent, making it ideal for this purpose.

Another thing bentonite clay is famous for? Occurring near fossil formations. The Morrison Formation, the geological formation where Dinosaur National Monument is found, is also heavily mined for bentonite clay. There have also been plenty of reports of kitty litter mining companies in Canada knowingly destroying fossil beds for more profit. So... your cat might be doing its business in dinosaur bits.

Third is diatomaceous earth. This fine white powder is frequently used as a cleaning product in the home. Applications of it can kill many types of insect infestations. The actual mechanism by which it does so is a little complicated, but it essentially dehydrates the insects to death. (Sometimes it's also used in kitty litter.) Diatomaceous earth is a sedimentary rock composed entirely of fossilized diatoms, a type of ocean-going microorganism that grows a silica-based shell.

Finally, there's good old-fashioned chalk. Chalk is simply an accumulation of the shells of tiny marine microorganisms, just like diatomaceous earth. Instead of being formed of silica-shelled organisms, however, it's formed out of calcite-shelled organisms known as coccolithophores. (Interestingly, the Cretaceous is actually named after the fact that more chalk was deposited around the world than during any other geological era—not, as you might expect, due to anything to do with dinosaurs.)

So, whenever your kids are drawing on the sidewalk with chalk, they're drawing with fossils.

My good friend Jeff Mann, the true Yard Ramp Guy, has asked me to revisit some of my original posts. This week in my From the Archives series: if it smelts fishy, it could be the remnants of the Stone Age. Or Bronze. Or Iron.

We’ve heard of the Stone Age, the Bronze Age, and the Iron Age. And yet, we aren't commonly taught why those ages occurred in that order. Which is just too bad, since it's pretty darn interesting.

The Stone Age has a simple explanation. Stone is easier to work than metal, and more common. We figured out how to use it first.

Ancient humans actually did master use of some metal during this time period — namely meteoric iron, a natural alloy of nickel and iron present in iron meteorites. We sometimes heated it but more often shaped it, by cold hammering, into tools and arrowheads; the stuff was quite difficult to work.

The ancient Inuit inhabitants of Greenland, though, used iron much more extensively than other Stone Age people. Greenland has the world's only major deposit of telluric iron, also called native iron, which is iron that occurs in its pure metal state.

Looking for the right tool to advance our evolution

Native copper, however, is found worldwide (as are native gold, silver, and platinum, all of which are of limited use for tools.) The hardest and strongest common native metal on Earth, copper proved one of the most useful.

Eventually we learned to smelt metals from ore and, around 2500 BC, learned to alloy the two together to make bronze, kicking off The Bronze Age. Tin was somewhat rare outside the British Isles, parts of China, and South Africa, so it actually ended up commanding prices higher than gold in many regions. We frequently used zinc, more common than tin, to produce brass.

Iron smelting first occurred circa 1800 BC but didn't become common until 1200 BC. Eventually, of course, iron became the metal of choice for civilization—it's just much stronger than most of the other options.