16 September 2008


One of the most frequently asked questions we get here at the La Brea Tar Pits is one so deceptively simple sounding that it regularly stumps us out of sheer, monosyllabic force. It's not that we don't have an answer -- it's just that the answer is exponentially longer and more complicated than the question.

That question, of course, is "Why?" Why, with a collection of more than 3.5 million fossils, do we keep digging? Don't we have enough fossils? Do we really expect to find anything new?

Some of the answers to these questions, in reverse order, are:

1) We find something new every week, if not every day. Not a new species necessarily, but things like a new and uniquely laid out deposit of fossils (such as our two associated sloth scapulae), or new information on the geology of the deposit. Mini-discoveries like these help color our continually evolving picture of the Pleistocene in Los Angeles. Now, new species are difficult to come by, but with this new project, we have sheer volume on our side. With the amount of fossiliferous dirt we have to dig through, we'd be surprised if we didn't discover a new type of animal.

2) You can never have enough fossils.

3) Now, the big question -- the big "WHY?" There are far more answers to this question than we could possibly cover in one meager blog entry, and many of which we hope to touch on in coming months. As for now, you'll have to settle for this lovely and informative graphic put together by one of our most dedicated volunteers, Tara Thara:

Click on the diagram above to be taken to Many Eyes website, where you can play with the image a bit more extensively. Currently, we're looking at the age of individual vertebrae organized by taxon; if you click through to Many Eyes, you can change that to compare, say, age by depth, or taxon by grid, etc etc.

Man, computers are great. One of the many many reasons we have to keep digging is because with statistical comparisons like the bubble diagram above (created from our Pit 91 Vertebrae Database), the more data, the better. In this chart, we're using the ontogenetic age (the developmental age of the bone) of different vertebrae to generate an estimate of how many very juvenile, juvenile, sub-adult, and fully adult animals we have in Pit 91. And from that information, we can make inferences about the animals' behavior in life. For instance, the large number of sub-adult saber-toothed cats found at Rancho La Brea has led some (such as my boss, Chris Shaw) to believe that Smilodon was a social animal -- the young cats would have gone after a trapped herbivore in the tar pits with their fully grown relatives, and all gotten stuck at the same time.

Now, the caveat to this -- the idea that more data creates more reliable statistics -- is that the dataset must be somewhat complete. Pit 91 hasn't been totally excavated yet -- we've got another 3-8 feet of asphalt to dig through, which equals tens of thousands of more fossils to find -- and we won't be able to make any final conclusions until we're done. On top of this, the database itself isn't complete; again, we have thousands of fossils that have been excavated and identified, but still need their data entered into the computer. However, with Project 23, we're hoping to enter the information into a computerized database as we dig. And since we'll be digging year-round with a much larger staff (as opposed to 12 weeks in the summer with a staff of two) we'll be able keep on top of data entry, and we'll be able to finish excavating each deposit in a much timelier fashion (i.e. under than 30 years).

So that, readers, is one of many reasons why we must keep digging. Population studies demand more data! Databases demand more data entry! And basic human curiosity demands that we slowly, steadily, someday reach the bottom of our inverted Everest.


Spencer said...

My favorite is Number 2!

pennjensen said...

I was struck by news accounts of findings that pointed toward a glimpse of the underlying ecology, or bio-pic (that's a pun) of the era, or an era, in which Zed met his demise. Crustacea, flora, a possible stream bed, etc.

Who among the bloggers or writers among you has more to share about the "big picture" of post-glacial, pre-human Wilshire Blvd?