Checked · The Architect Question
Sea level was 134 metres lower. What that does and does not explain
The claim
The evidence for a lost prehistoric civilisation is underwater, because sea level rose after the ice age and drowned the coasts where people lived.
Our verdict
CandidateThe sea level part is solid and larger than most people think. It was about 134 metres lower at the Last Glacial Maximum, and the coasts people would have lived on are genuinely submerged. What it explains is why we should expect gaps. What it cannot do is fill one.
This is the strongest argument on its side, it is routinely understated by the people making it, and it still does not do what they need it to do.
The number
Sea level at the Last Glacial Maximum was about 134 metres below present. The main phase of deglaciation ran from roughly 16,500 to 8,200 years ago. That is not an estimate from one site; it is a global reconstruction from around a thousand observations.
Lambeck, K., Rouby, H., Purcell, A., Sun, Y., Sambridge, M. (2014), Sea level and global ice volumes from the Last Glacial Maximum to the Holocene, PNAS 111, pages 15296 to 15303. DOI 10.1073/pnas.1411762111. Based on about 1,000 sea-level observations worldwide.
An early draft of book 4 said "something like 120 metres", from memory. The paper says about 134. Note the direction of that error: the remembered figure understated the argument it was being used to support. Motivated errors do not usually run that way, which is exactly why nobody catches them.
What it legitimately explains
People live on coasts. They always have, because coasts have food, water, transport and trade. A large fraction of the habitable land of the late Pleistocene is now under water, along with whatever was on it.
So the observation that we have relatively little coastal archaeology from before 10,000 years ago is not evidence that nobody was there. It is exactly what a submerged coastline predicts, and anyone reasoning from the absence of coastal sites to the absence of coastal people is making an error.
This is a real and often badly answered point. The correct response to it is not dismissal.
Where it stops
What the argument establishes
A large area of habitable coastal land is now submerged, and the figure is about 134 metres of vertical rise.
We should therefore expect the prehistoric coastal record to be sparse and biased.
Absence of evidence from that specific zone is weak evidence of absence.
Underwater prehistoric sites do exist and are found, so the zone is not empty in principle.
What it cannot establish
It is symmetric. The same submerged coastline hides ordinary hunter-gatherer camps just as well as it hides anything else, and there were vastly more of the former.
It predicts a gap, not a content. Nothing about the drowning tells you what was drowned.
The inland record is not submerged, and it is dense, continuous and shows no advanced civilisation.
A civilisation of the kind proposed would have inland traces: quarries, mines, trade goods, agriculture. Those are not underwater.
That last column is the whole answer. A blind spot is a reason to withhold judgement about what is inside it. It is never a reason to believe a specific thing is inside it, and the specific thing being proposed is one that would have left marks outside the blind spot as well.
We take this seriously because we have the same problem. Our own lidar detector is blind to pond barrows: it cannot see a depression at any setting, and it scored zero on five of them. That blindness is a real limitation and a measured one. It would not license us to claim that the ground is full of undetected pond barrows.
Where this leaves things
The five labels, applied to this question. Nothing is left unlabelled.
Sea level at the Last Glacial Maximum was about 134 metres below present, and the main deglaciation ran from about 16,500 to 8,200 years ago.
A large area of habitable late Pleistocene coastline is now submerged.
Any specific submerged site. Underwater prehistoric archaeology exists and is worth funding.
The inference from a submerged coastline to a specific lost civilisation. The gap is symmetric and predicts nothing about its contents.
Reconstructions of what the drowned coasts held.
Sources
- Sea level and global ice volumes from the Last Glacial Maximum to the Holocene. Lambeck, K. et al., PNAS 111, pages 15296 to 15303, 2014.
Related
Where this is argued in full
Answering the Architect Question
Both cases at the same length, measured and printed at the back. The argument runs across four papers in one journal and you can read all of it.
Both cases at the same length, measured and printed at the back. It is written and not on sale, and advance readers can read it first.