Mursi Astronomy II

Mursi Man. Photo by CharlesFred.

Yesterday I introduced the Mursi calendar, which might not be very good but was good enough for the needs of the Mursi. While it is ostensibly a lunar calendar, in reality agricultural activity is decided by close examination of the local environment rather than astronomy. This creates a flexible calendar which adapts to the variability of the Ethiopian climate. Today I’ll talk about a second problem. While most of the Mursi schedule is flexible, the flooding of the River Omo, at the edge of Mursi territory, is an annual and more or less fixed event.

According to the locals the Omo floods four times. Timing the planting of the sorghum crop is therefore crucial. Plant to early and the floodwaters will wash the seeds away. Plant too late an you may have missed your chance to grow sorghum on the river bank this year. This is critical as Ethiopia is not currently known for its bountiful landscape.

The flooding of the Omo is related to the thawing of snow in the nearby mountains. This causes the problem of timing, because this flooding is related to the solar cycle and so cannot be measured in the lunar cycle the Mursi use to measure the year. While a chaotic calendar may work for most of the year it would seem in this period, around August to October, accurate timing is necessary. How is this achieved when the calendar is based on the age of a bergu (goat – see yesterday’s post) that no-one agrees about? After living with the Mursi for a while David Turton found some of the men had a hobby, sun-watching. They would find their own place in the landscape to watch the sun and pass this knowledge down to their suns. Following one man Turton found the sun had two houses it rested in, one by one mountain, the other house by another. He had found people who were watching for the solstices, though this would leave no archaeological trace in the landscape. The problem appeared to be solved. These men could be experts on the bergu, by bring their experience of astronomical observation. His informant told him. The sun rests in his house there in the first half of bergu 5 and then travels to his house there where he rests in first half of bergu 11. Like much of the Mursi calendar, this didn’t quite make sense. It couldn’t always be the first half of bergu 5 that the sun rested, because there are 12.5 lunar cycles in a year. Sometimes it must the second half of bergu 5. No, replied his informant. The sun always rests in its house in the first half of the bergu. This defies celestial mechanics.

And so one solstice Turton observed the sun, but it wasn’t in its house in the first half of bergu 5. It had already been in its house in the second half of bergu 4. He mentioned this to informant. “Yes, the sun arrived early this year. It does that sometimes.”

For a western astronomer this is unthinkable. We measure our days against the sun so the solstice cannot arrive early or late. It’s a fixed cycle. For the Mursi there is no solar cycle. The sun is subject to seasonal whims like the flowering of plants or the flight of birds. To say they have a ‘primitive’ astronomy is missing the point. It’s more that they reject the basic assumptions westerners make in astronomy. Given they were living this way till the 1980s then it’s also a poor judgement to say the calendar is primitive at all. It’s fitted their way of life perfectly.

So how do they get to river in time for the final flood?

Another observation they make are the settings of four stars in the evening twilight. As each star in this sequence disappears into the sunset sky, the river floods. From the western point of view this makes sense. The melting of the snow is driven by the solar cycle. The heliacal setting of a star is also a product of the solar cycle so there is a clear correlation between the two events. Is this the Mursi calendar? No.

The Mursi don’t recognise a correlation. They see the setting of the stars as a causation. At the stars are consumed by the sun so they melt, giving rise to the flooding of the Omo. Just like the plants or sun, so the stars too could set earlier or later than expected. There’s no intentional high accuracy.

The reason I find this so interesting is that if this belief left archaeological traces then we would assume there was high accuracy. Heliacal rising is accurate to a few days, so if they left something pointing to the sun when it swallowed the stars we’d assume accurate observation of four dates. A date is something which occurs at the same time each year. An annual event might happen each year but the timing could vary considerably. In this case the remains would really be records of observations of events not dates because the Mursi don’t have a calendar capable of planning for dates (by western reckoning). The only accuracy in the remains would be the accuracy Nature provided rather than from human planning.

If you take this example elsewhere then it makes interpreting places like Stonehenge a lot harder. There is a tradition that Stonehenge is a computer for calculating dates. If it was a site for observing events would it look any different? Approaching from the Avenue the stone circle would mark the southernmost limit of the setting sun. This is a physical boundary and you wouldn’t need an accurate calendar to mark this any more than you need to know the period of pendulum to mark it’s widest points in its swing.

The example of the Mursi cannot be simply dropped on to other sites. I’m not suggesting that bringing a guy from 20th century Africa will give you all the answers at Stonehenge. What it does do is show another way of seeing things and remind you that when you look at these places you could be dead wrong. It helps if you can justify assumptions you make about a site.

Other Mursi links: Exciting news from Mursiland, suggests the Mursi way of life before the 1990s may soon be a lost memory. This is ethical territory I’m ill equipped to deal with. If you modernise the tribe do you give them benefits that others have like better medicine, or is this colonisation?

There’s also a recent story that the Mursi may be moved to protect wildlife from the Washington Post (via FieldNotes). —–