1In today's class I'm going to talk about marine archaeology,
2the branch of archaeology focusing on human interaction with the sea, lakes and rivers.
3It's the study of ships, cargoes, shipping facilities, and other physical remains.
4I'll give you an example,
5then go on to show how this type of research is being transformed by the use of the latest technology.
6Atlit-Yam was a village on the coast of the eastern Mediterranean,
7which seems to have been thriving until around 7,000 BC.
8The residents kept cattle, caught fish and stored grain.
9They had wells for fresh water,
10many of their houses were built around a courtyard and were constructed of stone.
11The village contained an impressive monument:
12seven half-tonne stones standing in a semicircle around a spring,
13that might have been used for ceremonial purposes.
14Atlit-Yam may have been destroyed swiftly by a tsunami,
15or climate change may have caused glaciers to melt and sea levels to rise, flooding the village gradually.
16Whatever the cause, it now lies ten metres below the surface of the Mediterranean,
17buried under sand at the bottom of the sea.
18It's been described as the largest and best preserved prehistoric settlement ever found on the seabed.
19For marine archaeologists, Atlit-Yam is a treasure trove.
20Research on the buildings, tools and the human remains has revealed how the bustling village once functioned,
21and even what diseases some of its residents suffered from.
22But of course this is only one small village, one window into a lost world.
23For a fuller picture, researchers need more sunken settlements,
24but the hard part is finding them.
25Underwater research used to require divers to find shipwrecks or artefacts,
26but in the second half of the twentieth century, various types of underwater vehicles were developed,
27some controlled from a ship on the surface, and some of them autonomous,
28which means they don't need to be operated by a person.
29Autonomous underwater vehicles, or AUVs,
30are used in the oil industry, for instance, to create maps of the seabed before rigs and pipelines are installed.
31To navigate they use sensors, such as compasses and sonar.
32Until relatively recently they were very expensive, and so heavy that they had to be launched from a large vessel with a winch.
33But the latest AUVs are much easier to manoeuvre -
34they can be launched from the shore or a small ship.
35And they're much cheaper, which makes them more accessible to research teams.
36They're also very sophisticated.
37They can communicate with each other and, for example,
38work out the most efficient way to survey a site,
39or to find particular objects on the seabed.
40Field tests show the approach can work.
41For example, in a trial in 2015,
42three AUVs searched for wrecks at Marzamemi, off the coast of Sicily.
43The site is the final resting place of an ancient Roman ship,
44which sank in the sixth century AD
45while ferrying prefabricated marble elements for the construction of an early church.
46The AUVs mapped the area in detail, finding other ships carrying columns of the same material.
47Creating an internet in the sea for AUVs to communicate is no easy matter.
48Wifi networks on land use electromagnetic waves,
49but in water these will only travel a few centimetres.
50Instead, a more complex mix of technologies is required.
51For short distances, AUVs can share data using light,
52while acoustic waves are used to communicate over long distances.
53But more creative solutions are also being developed,
54where an AUV working on the seabed offloads data to a second AUV,
55which then surfaces and beams the data home to the research team using a satellite.
56There's also a system that enables AUVs to share information from seabed scans, and other data.
57So if an AUV surveying the seabed finds an intriguing object,
58it can share the coordinates of the object - that is, its position -
59with a nearby AUV that carries superior cameras,
60and arrange for that AUV to make a closer inspection of the object.
61Marine archaeologists are excited about the huge potential of these AUVs for their discipline.
62One site where they're going to be deployed is the Gulf of Baratti, off the Italian coast.
63In 1974, a 2,000-year-old Roman vessel was discovered here, in 18 metres of water.
64When it sank, it was carrying medical goods, in wooden or tin receptacles.
65Its cargo gives us insight into the treatments available all those years ago,
66including tablets that are thought to have been dissolved to form a cleansing liquid for the eyes.
67Other Roman ships went down nearby, taking their cargoes with them.
68Some held huge pots made of terracotta.
69Some were used for transporting cargoes of olive oil, and others held wine.
70In many cases it's only these containers that remain,
71while the wooden ships have been buried under silt on the seabed.
72Another project...