The answers!

So here are the answers to Tuesday's quiz on the human past, in chronological order:

1. Our ancestors began walking on two legs by 6 or 7 million years ago. The earliest fossil species of hominin (bipedal members of the Hominidae family) that looks like it walked upright is called Sahelanthropus tchadensis.

2. The oldest evidence for stone tools dates to 3.3 million years ago (mya) in Ethiopia and was just published a few months ago. The evidence consists not of the stone tools themselves, but rather animal bones with cut marks on them that could have only been made by stone tools. Thus we have indirect evidence that hominins were butchering animals with stone tools 3.3 mya. The cut marks were probably made by Australopithecus afarensis (one of Lucy's species).

3. The first fossil hominin that is generally attributed to our genus (Homo) is Homo habilis who lived in Africa between 2.4 and 1.8 mya (although some now argue that Homo habilis should be re-classified as an Australopithecine).

4. The first people left Africa by 1.8 mya. And people I don't mean fully modern humans, I mean another species of humans: Homo erectus. Modern humans didn't leave Africa until just 100,000 years ago.

5. Humans first colonized Europe by about 1.2 million years ago - but once again these were not modern humans, they were Homo erectus - a subgroup of which eventually evolved into Neanderthals. Modern humans didn't show up in Europe until about 40,000 years ago.

6. The earliest evidence for use of boats in indirect and dates to about 1 mya. There is a site on the island of Flores in Indonesia that has never been connected to mainland Southeast Asia by land and yet, there is a site there with clear stone tools dating to 1 mya - tools that were definitely made by humans. It is inferred by many archaeologists that Homo erectus somehow made it to Flores Island by floating on rafts or simple boats, however, this is debated. For those who don't like that evidence, the next best thing is also indirect and based on the fact that modern humans made it to Australia, Papua New Guinea, and other islands by 40-60,000 years ago.

7. The first evidence for control of fire dates to 800,000 years ago at a site called Gesher Benot Ya'aqov in Isreal. It was Homo erectus who was living there and using fire. However, many anthropologists believe that Homo erectus must have been able to control fire long before this date. Controlling fire would have helped Homo erectus see in the dark, stay warm in cold places outside Africa, have protection from predators, and cook their food - allowing them to eat more calories and feed their big brains. Unfortunately it's hard to find evidence for controlled fires.

8. The first Homo sapiens appeared in Africa about 200,000 years ago. The oldest specimens have been found in Omo, Ethiopia.

9. The first art (depending on how you define art) is a piece of red ochre with incised lines on it from Blombos Cave, South Africa and is about 100,000 years old.

10. The first clearly intentional burials have been found in Israel and date to 100,000 years ago - these are burials of modern humans. It appears that a few Neanderthals did bury their dead, but the Neanderthal burials aren't as old as the oldest modern human burials.

11. People first arrived in Australia between 40 and 60,000 years ago (I sort of already answered that one). The first occupation of Australia is notoriously difficult to date. It falls right around the limits of radiocarbon dating and many sites have disturbed stratigraphy making luminescence dating difficult.

12. Neanderthals went extinct by 30,000 years ago - although possibly a little earlier, at least in some places. Although now there is some pretty good DNA evidence that a few of them interbred with modern humans 100,000 years ago in the Middle East - so some of the genes may be living on in us (check out this awesome 17 min TED talk about the human genome project by Svante Paabo). But I don't think there is any doubt that most of them went extinct.

13. The Denisovans lived about 30,000 years ago at a site called Denisova is southern Siberia. A pinky bone was found at the site and the researchers were able to extract DNA from just a couple of years ago. They were trying to determine if it was Neanderthal or modern human, but it turned out to be neither! All we really know about them is that they were another human species, more closely related to Neanderthals than to ourselves, and that it seems that they did interbreed with some modern humans. It will be exciting to hear if more bones are discovered in the future.

14. People first arrived in the Americas by 14,000 years ago. It's definitely possible they were here a little earlier, but at the moment the oldest sites are Monte Verde in Chile and Paisley Caves in Oregon.

15. The earliest evidence of agriculture is about 11,000 years ago in the Middle East.

So there is my crash course in the human past. You should remember that these things are all hotly debated, new discoveries and new scientific techniques are always helping us refine what we know about the past - and you should remember that I am not an expert on any of these things - I work in Alaska!