“All the better to smell you with, my dear”

We now have another piece of empirical evidence that we didn’t just zap into existence in full cognitive flower in a fit of creative ideation.

In fact, it was our growing ability to smell the flowers, and the small creatures who fed on them, that led the way in the development of the mammalian brain — eventually, our brain.

The evidence, from a recently-publicized study of 3-D CT images of the brain cases of two pivotal species, shows that the first part of the brain to undergo a dramatic increase in size was the area associated with olfactory sensation.

It seems that we smelled well before we thought well, and this is just one more piece in a growing body of research that is slowly chronicling the physical steps in the development of our thinking brain.

As Jerry Coyne pointed out again and again in Why Evolution Is True (reviewed here recently), new evidence can be compared to the expectations which arise from ID and evolutionary versions of human development. If there had been a Special Creation, there would have been no need for an incremental growth in the brain’s ability to process sensory data. But if we have developed by evolutionary means, this latest discovery fits perfectly into what the theory of evolution predicts: intermediate and transitional forms with new features built upon and growing out of existing features.

Also typical is the way that new investigative technologies open areas of understanding that had been closed to all but speculative interpretations. Indeed, these unexaminable areas are the favourite hunting grounds for fundamental literalists, who swarm like crows after roadkill over any contentious areas within evolutionary research, then falsely claim that evolution itself is contentious.

Now, with CT scanning, it is possible to measure the brain cases of rare fossil skulls without destroying the fossils in the process. So it’s only now that a truly concerted effort can be made to trace the evolution of varying parts of the emerging mammalian brain.  As R. Glenn Northcutt wrote in Science:

Speculation about the evolutionary steps leading to large and complex mammalian and avian brains is equally contentious and unresolved, in part because of the rarity of fossil skulls and, until recently, the need to destroy such skulls in order to expose the endocasts (casts molded by the cranial cavity). Typically, endocasts are the only record of the brain’s outward appearance in a transitional form, because brains themselves are rarely fossilized.

As Discover magazine explains, the researchers looked at two carefully-chosen animals:

The researchers looked at fossil skulls of two ancient animals. The 205-million-year old  Morganucodon was a proto-mammal: a reptile with some decidedly mammalian characteristics (it looked a bit mouse-like, researchers say), that is thought to be an ancestor of mammals today. The tiny mammal Hadrocodium—imagine a shrew the size of a paperclip—lived 195 million years ago. …

Based on the size and shape of the skull cavity, and the impressions left by brain tissue, the researchers could make detailed models of the animals’ brains. Morganucodon‘s brain was 50% larger, relative to its body size, than the brains of the ancient reptiles. Most of this was due to a huge size increase in the olfactory bulb and olfactory cortex, brain areas responsible for smell. Other parts of the brain grew somewhat, as well, and began to look a little more like the brains of modern mammals. When the researchers looked at Hadrocodium’s brain, they found it had grown another 50%, compared to Morganucodon’s. Again, much of this increase was due to larger olfactory regions.

“Until now, we could only speculate what changes were occurring and at what rate. Now we have data and can infer what selective pressures were driving brain evolution in the radiation that led to mammals,” Northcutt, who wasn’t involved in the study, told ScienceNOW.

Victoria Gill explains, in BBCNature, that “An improved sense of smell may have allowed our tiny, furry ancestors to hunt at night … which meant that they could avoid competing for food resources with dinosaurs that shared their habitats.”

Gill quotes Dr. Zhexi Luo from the Carnegie Museum of Natural History in Pittsburgh, who was involved in the study: “Our mammal ancestors didn’t develop that larger brain for contemplation, but for the sense of smell and touch.

“But thanks to these evolutionary advancements, which gave mammals a head start toward developing a large brain, humans some 190 million years later can ponder these very questions of natural history and evolution.”

It’s worth noting that this research is consistent with the evolutionary explanations of the development of consciousness outlined by Antonio Damasio in How Self Comes to Mind (reviewed on this blog recently here and here.). First came physical sensations, then an organic emotional reaction to those inputs, and only later self-aware reflection on our experiences. While other species are stuck somewhere along the sense and reaction line, as Zhexi Luo noted, we have somehow developed the ability to step “outside” the sense-reaction interaction and experience life on an “autobiographical” and rational level.

Well, at least sometimes we can.

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One thought on ““All the better to smell you with, my dear”

  1. A lot more would be needed to support this contention , for example about the environment in which this aspect of evolution took place thinking of the mammals who have super developed sense of smell.

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