A few years back I was discussing Denisovans in Wallacea: here’s the map again. 
Cooper and Stringer were suggesting that Denisovans had colonized some or most islands in Wallacea, and that explains Denisovan ancestry in populations there today (Philippine Negritos and Melanesians). I thought it a bit unlikely because it meant that Denisovans had to have had seagoing technology, but in a very narrow range: good enough to reach Wallacea (and the Philippines), but not good enough to reach Sahul (Australia/New Guinea). I was wrong: it now looks to be true. Since that article people have found good evidence of early settlement in the Philippines , also in Sulawesi, as well as Flores. Some of those are older than Denisovans, likely erectus.
Look at the glacial-max map of the Philippines and environs, when sea level was 120 meters lower than today: 
You can’t walk to the Philippines, but the water gaps are not very wide, on the order of 10 kilometers. I don’t much believe in breeding colonies being founded by tsunamis – note that only a few placental mammals ever succeeded in crossing, as pointed out by a commenter – but I can imagine someone paddling a log across those narrow gaps. The required crossing for Sulawesi is also narrow.
Elephants are pretty good swimmers and can cross that kind of gap, and various kinds of elephants colonized the Philippines, Sulawesi, and Flores. There’s a known example of an elephant that swam ashore after being washed overboard 48 km off the South Carolina coast in 1856.
But why didn’t early humans make it to Australia back then? Two thoughts: that would have required multiple sea crossings, some considerably wider that the ones leading to the Philippines or Sulawesi. Maybe that was enough to prevent it. Second, some of the islands in the proposed paths were small. Even if some population managed to settle one, it may have been too small to succeed for long. There was an island between Tasmania and the mainland that was inhabited for a few thousand years after rising waters cut the connection with the Australian mainland, with a population around 400. And then it wasn’t inhabited anymore: something happened.
West Hunter 
I’m confused. Isn’t the point of the Reich article to discuss Denisovan-like ancestry in Australia/New Guinea? (In fact, Reich actually uses New Guinea as his benchmark for comparisons of Denisovan ancestry in other places.) Did this DNA arrive in a later, unrelated expansion, or something?
Incidentally, how do we distinguish a colony of Denisovans from a colony of anatomically modern humans with some amount of Denisovan admixture? Europeans have about 4% Neanderthal DNA, but Jamestown obviously wasn’t a Neanderthal settlement.
The site in the Philippines dates to 700,000 years ago. Early for Denisovans, way too early for modern humans.
Most likely Homo erectus, then?
Homo habilis, as in Flores of same period at Mata Menge, via coracles, which Homo erectus at Java &Peking did not have.
So you were there.
If early people had watercraft, why did hominins not island hop to Australia or PNG before 65kya?
Pretty impressive to think of erectus building rafts or canoes or even paddling logs around.
Per Wikipedia, “For an observer on the ground with eye level at h = 5 ft 7 in (1.70 m), the horizon is at a distance of 2.9 miles (4.7 km). ” So, they wouldn’t have been able to see the land on the opposite shore, when they were just standing on the beach, but, they wouldn’t have had to get very far above sea level to be able to see it was there. This website here, http://www.ringbell.co.uk/info/hdist.htm has an actual distance to the horizon calculator. At a mere 26 feet above sea level (including the distance from your feet to your eyeballs, you can see 6.2 miles, which is 10 km. Not hard to believe there are plenty of places with at least that much elevation from which they could have seen the opposite coast. Of course if they were using logs/dugout canoes/rafts for fishing, they might have gotten far enough out to spot the land even from the surface.
And there is an optical effect called a fata morgana which can make objects visible over the horizon.
I’ve seen a claim that from the mountains on the NW peninsula of Iceland the mountains of the E coast of Greenland can sometimes be seen because of an optical effect. Does anyone know whether it’s true?
Hillingar effect: true.
Thank you, Mr C. For everyone else who finds the Vikings fascinating:
Click to access Polarforsch1979_2_5.pdf
If I had any excuse I’d mention sunstones and Iceland spar, but I don’t.
Here’s an excuse – do tell.
Sunstone
Do note the A. Wegener they cite so much 🙂
And Hy-Brasil?
I like Avalon better. “Straight down the balustrade tumbled a cliff, which was of glass. From above he could see how the grottos broke light into a million rainbow shards, spraying the light outward again, hot sparks of red and gold and violet. The sea beneath had been so dark it was almost purple, with foam of amazing snowy whiteness where the cliff plowed the water… for Avalon stayed never in one place, the island floated over the western ocean in a haze of its own magic…”
Arthur’s Avalon could have been the Roman fort at Aballava/Avalana on the Solway coast near the western edge of Hadrian’s Wall.
I owe this morsel to Graham Robb’s 2018 book The Debatable Land, which is a good read – particularly for his proposed sorting out of Ptolemy’s second century map of the British Isles.
“Pretty impressive to think of erectus building rafts or canoes or even paddling logs around.”
I think this may also tie into the many “fleeing from war” founding myths – if people are being chased they’ll take bigger risks then they would do normally..
We are not chimps, we people can swim. If I can see the other side from a low hillock, I would try to cross over swimming. For a number of urgent reasons. I could even swim back to bring in my fiancee.
Early humans were drawn to beach combing. All kinds of scumptious sea critters just waiting in the shallow seas for a hominid to come along with a shell smashing rock to enjoy endless fine dining. It is really too damned bad that the evidence of their existence has long been destroyed and covered up by up to 300 feet of ocean. All over the map shown by Cochran there has been detection of turtle shells getting a lot smaller presumably because of hunting.
I have done a fair bit of reading on hominids and I have come up with two conclusions. They were a lot smarter than the experts thought they were and the experts are a lot dumber than they themselves think they are. They were damned crafty and ingenious going way back in time. They have earned the trademark Cochran disdain for believing stupid stuff.
I won’t go into a long list of how the experts keep assuming dumb stuff about early humans, just one example. Berger and Hawks have done a fine job on Homo Naledi but I have read multiple examples by other experts that these small brained fellows were not smart enough to control fire. Well, if they didn’t control fire there is no way in hell they could have explored the depths of that cave so they must have evolved bat radar. No, they didn’t say that, they say these grapefruit size brained little guys were incapable of controlling fire and they obviously were. It’s like the experts visualize the face of these hominids and say, apelike, dumb, couldn’t build a raft, couldn’t figure out all kinds of ingenious ways to eat well and live better. Well they did get smart enough to spread out from Africa millions of years ago but they lived in environments that sadly remove virtually all trace of their existence.
Not everyone in a group needs to be smart enough to figure things out, or even understand them well enough after they are found/discovered/invented. They only need to be smart enough to understand by gesture “Hold this.”
A wild crow smart enough to imitate human to use a credit card to buy train ticket. https://www.youtube.com/watch?v=Dh7bOXCzukA
I saw film of one of those Japanese crows that had a neat way of cracking tough nuts. Leave them on the road at a traffic light. Then wait on the light for a vehicle to run over a nut cracking it. Then wait until the light turns red before collecting its contents.
Given the adaptations that the Bajau exhibit after 500-1k years of a marine lifestyle, couldn’t we expect there to be a beachcomber Denisovsn race that was supremely adapted to swimming? Couldn’t they have had 100k years to adapt? Maybe swimming 10 km was nothing for them.
In the old days of African exploration, chimps were sighted by Europeans carrying torches. Its a small step from foraging after bushfires, to playing with fire as a tool. But not lighting or maintainng it.
That means that one can see the top of a 26′ tall tree from the beach.
@dlr: The horizon distance works in both direction, in that it is cumulative from the observer’s eye to the horizon, ADDED TO the horizon distance of the thing-being-observed. Land past the horizon is not AT sea level, it is ABOVE it, so it will be seen from OVER the (optical) horizon.
Standing on a 20-foot hill (on your tiptoes, perhaps) with your eyes at a 26-foot elevation, the (optical) horizon is 6.2 miles. However, if the land over the horizon has a 30-foot hill with 15-foot trees growing on top, the treetops are at 45 feet elevation. From 45 feet, the horizon is 8.2 miles, meaning you could see the tops of the trees if you were swimming at sea level (i.e., ZERO elevation). But, when your eyes are at 26 feet on your hill instead of being eyeballs deep in the ocean, you’re adding 6.2 miles (horizon from 26 feet) to 8.2 miles (horizon from 45 feet)–so you could see the tops of the 15-foot trees on that 30-foot hill from your vantage point at 26-foot elevation from over fourteen miles*.
Obviously, you’ll see Mount Fuji over-the-horizon from MUCH farther away that you’d see a small hill. Just like you can see the sun as it breaks over the horizon, even though it’s 93,000,000 miles away.
Expanding the range is great because it naturally means more dig sites.
Makes me wonder about Japan: it was probably either connected, or pretty darn close to it. But no evidence yet, huh? I’m still crossing my fingers for a complete skull. I think everyone wants to see a face with those chompers.
Slightly off topic here but I haven’t found a recent topic here to inject the question:
concerning the demise/replacement of Neanderthals and Denisovans by Homo Sapiens, a big component for an invasive species to displace the natural species of a region is the ability to reproduce faster than the competition. Would there be any validity to the idea as with Homo Sapiens reproductive capacity being far higher than the others, in particular a naturally higher occurrence of estrus as with ~ 12 times per year for modern humans as opposed to a possible once per year/season for the Neanderthal et al?
Any evidence or research for this (so far personal) theory?
No.
Flores is where the Hobbits showed up hundreds of thousands of years later….Any possible connection?
I know one case of the small population on a small island being wiped out. Twice.
“North Rona … is the most remote island in the British Isles to have ever been inhabited on a long-term basis. … the entire population of thirty died shortly after 1685 after an infestation by rats … which reached the island after a shipwreck. The rats raided the food stocks of barley meal and it is possible the inhabitants starved to death, although plague may have been a contributory factor. … The rats themselves eventually starved to death, the huge swells the island experiences preventing their hunting along the rocky shores. It was resettled, but again depopulated by around 1695 in some sort of boating tragedy …”
(WKPD)
@ Greg Cochran:
Your post mentions the land bridges exposed during ice age periods of lowered sea level (here and in your posts about Beringia).
In addition, one of your April posts mentions “early layers” of settlers in the New World and the evidence that there are significant genetic links to Australasians among some tribes in South America.
The discussion of new migration avenues exposed by lowered sea levels makes me wonder if there are now-submerged islands/island chains in the southeast Pacific that served as intermediate (and livable) landing points for “pseudo-Andamanese” for an ice age migration to the New World. Such islands–which would be seamounts today–could have significantly shortened the distances necessary to migrate to the west coast of South America, perhaps turning it into a series of migrations.
Since there’s no sign of any ancient inhabitants in Polynesia, by which I mean no sign, I think that’s the wrong line of thought.
A dopey take on Reich’s book over at Scientific American:
“Plug and Play” Genetics, Racial Migrations and Human History
We’re all just alike under the skin, except for the minor part of genetic variation that gave me a 20-point IQ edge over this bozo. Make it 30: he’s dead wrong about his specialty.