Oct 26 2018

Laser Scanning Archaeopteryx

Published by under Evolution
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My favorite fossil is the Berlin specimen of Archaeopteryx lithographica, for several reasons. First, it is straight-up a beautiful fossil, well-preserved, and just a natural work of art. But this is no object of human creativity – it is also a wonderful transitional fossil, catching evolution in the act of transforming theropod dinosaurs into birds. There is a cast of the Berlin specimen at the Peabody museum in New Haven, and it is capable of capturing my attention even in the middle of the hall of dinosaurs.

Recently I was able to visit the Natural History Museum (NHM) in London – where they have the original fossils of the first Archaeopteryx specimen found in 1861 (before the Berlin specimen), making it the type specimen. It too is beautiful, showing both the plate and the counterplate – the limestone that contains the fossil was cracked open, revealing impressions and fossils on both sides.

You can clearly see the feather impressions surrounding what at first looks like a small theropod dinosaur. On closer inspection, however, there are bird-like features as well, but retaining things like teeth and a long bony tail not seen in birds. Again – a dramatic transitional fossil, clearly connecting birds to what are now called non-avian dinosaurs (because birds are dinosaurs).

Creationists have long tried to argue that Archaeopteryx is not transitional, just a weird bird, but the evidence is undeniable. It has as close to halfway features between walking theropods and modern birds as you can get. But to be clear, Archaeopteryx is not on the direct line to birds. It is a side branch from a period in time when small feathered dinosaurs were undergoing adaptive radiation, only one branch of which would lead to modern birds. This is always going to be the case, however, and does not diminish the transitional significance of this species. Also, in recent decades a number of feathered dinosaurs have been discovered, fleshing out much of the evolutionary pathways between theropods and birds.

So some creationists have resorted to another tactic – claiming the specimen is a forgery. Famously, astronomer Fred Hoyle argued that the London specimen was a fraud, and in 1986 even published an entire book to make this case. This became another famous example of why scientists should not step so boldly out of their area of expertise. It was also epic bad timing – right on the cusp of a wave of discoveries of feathered dinosaurs, including further Archaeopteryx specimens.

Creationists will also point to Piltdown man as an example of an established fraud, and use that to somehow bolster the case that any other fossil that is particularly compelling evidence for the branching descent of evolution is also a fraud. But this example shoots their own argument in the foot.

Piltdown man was questioned as a possible mistake (if not a fraud) when it was discovered. It had the peculiar feature of all the bony parts that would connect the human-like skull to the ape-like jaw being warn away. Further, Piltdown became increasingly out of step with other human fossils, because it was based on false assumptions about the path of human evolution. Eventually evolutionary biologists took a closer look at the actual bones (rather than just casts) and when they did easily confirmed the hoax.

The various specimens of Archaeopteryx are very different. First – they confirm each other. Piltdown was a one-off (if you include Piltdown I and II as one collection, all found by the same person, Dawson, at roughly the same time and location). No later finds showed the same features as Piltdown.

In contrast, the London specimen was later confirmed by the Berlin specimen. There are now 12 separate specimens of Archaeopteryx (although one is probably of a closely related genus). They all date to the upper Jurassic. Further, the bigger evolutionary picture has since been confirmed by many feathered dinosaur specimens from the same time period showing various stages of feather and bird evolution. The very fact that theropod dinosaurs in general have been shown to be feathered is confirmatory. This is all the opposite of what happened with Piltdown.

Further, as new techniques were developed the Piltdown specimens were shown to be a fraud. Recent analysis of the bones, including DNA analysis and careful morphological analysis, demonstrates that the ape bones came from a single orangutan specimen, while the human bones came from 2 or more specimens. Further, details of the forgery show consistent techniques used, meaning there was likely a single hoaxer, with a skill level appropriate for Dawson (who was almost certainly the hoaxer in this case).

The bigger point here is that forgers creating physical evidence, like fossils, cannot possibly account for later technological developments. Dawson could not conceive of our eventual ability to extract tiny amounts of DNA from very old bones.

Likewise, any alleged forger in 1861 could not possibly have anticipated modern techniques for analyzing fossils. When Hoyle made his outrageous accusations in 1985 the NHM reexamined their specimen. They found:

Microscopic investigations showed that hairline cracks in the feathers, invisible in the SLR images, could be matched up on the part and counterpart. Likewise, the branching of manganese crystals running through the rock.

The two halves of the fossil match up, including tiny cracks in the feather impressions. This would be impossible to fake today, let alone in 1861 before modern microscopes. A 19th century forger would not even think they had to make their fake work at the microscopic level. Hoyle should have stuck with astronomy, now his legacy includes shameful pseudoscience.

Recently the NHM has done another even more high-tech analysis. They have laser-scanned their specimen, creating an extremely detailed digital copy of the fossil. In many ways this is superior to the specimen itself, because the digital copy can be studied and manipulated in ways that cannot be done with a slab of rock.

What the researchers specifically did was take the two halves of the fossil and digitally put them back together. They found that the two halves match perfectly. This is a level of precision that would be impossible to fake.

The only reasonable conclusion based on all the evidence is that the various Archaeopteryx specimens are genuine. This means there were half-bird – half-theropod creatures flying around during the late Jurassic. I cannot emphasize enough what stunning evidence this is for the fact of common descent. Creationists have nothing left but mindless denial.

The NHM plans on laser scanning all their most precious fossils, and it’s likely this technique will be used more generally in paleontology. In fact you can already take VR tours of some museums, although they are still very limited at this time. I hope within a few years anyone with a good VR headset could tour museums around the world in great detail. I still prefer seeing the actual specimens, but a VR tour is better than no tour at all, and can have several advantages.

First – you can spend as much time as you want at any specimen, without waiting in line or holding up other viewers. Second, you can manipulate the specimen – zoom in, spin it around, play with it. Animations can show how the bones fit together, fill in missing pieces, and provide other educational information. High definition laser scans can be used not just for tourists, but also by scientists doing serious anatomical analysis. It can also be used as a basis for 3D printing, if you want a copy for display.

Laser scanning technology is good for more than just proving the fossils were not faked – but that is a nice side benefit.

 

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