Were Birdbrains on the Dinosaur Pre-flight Checklist for Evolution?

Despite the derogatory implication of “birdbrain,” birds’ brains are complex. Compared with reptiles, the volume of a bird’s brain, when compared to body size, is large. Also, in comparison to reptiles, the bird forebrain is proportionately large compared to the rest of the brain. The same is true of mammalian brains.

These digitally reconstructed endocranial casts represent the brains of Archaeopteryx (top) and a loon (Gavia immer, bottom). The dotted lines indicate the wulst—an indentation important for processing information and controlling muscles. The wulst is a feature of birds’ brains. Image: A. Balanoff et al., “Evolutionary origins of the avian brain,” Nature (31 July 2013) doi:10.1038/nature12424

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This woodpecker’s brain endocast, seen through a transparent skull, shows the typical large forebrain found in birds. Image: ©AMNH/A. Balanoff, www.mnn.com

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This endocast of the Archaeopteryx brain depicts the cerebrum (green), cerebellum (blue), optic lobes (red), olfactory bulbs (orange), and brain stem (yellow). Image: ©AMNH/A. Balanoff, www.nbcnews.com

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This brain endocast of the troodontid dinosaur Zanabazar junior is shown inside a transparent skull. This dinosaur is known for its proportionately large brain. The researchers believe that its brain was evolving flight-readiness that would suit some dinosaurs for evolution into birds. (Not much can be said about the rest of this dinosaur. The only parts in existence are this skull and partial jaw, several lower vertebrae, part of the pelvis and part of the right hind leg. It was classified as a Saurornithoides until reclassified by Mark Norell.1) Image: ©AMNH/A. Balanoff, www.bbc.co.uk5

The cerebrum, or “forebrain,” is the part of the brain most associated with processing information and coordinating voluntary activity. Bigger brains and forebrains imply “more highly evolved” to evolutionary thinkers. Evolutionists wonder how birds and mammals independently evolved brains that are “10 times as large, relative to a given body weight, as those of their ancestors”2 and especially how they evolved “hyperinflated forebrains.”3

The Better To See You With, My Dear

One theory is that evolving sensory improvements provided a survival advantage. An improved sense, like smell or vision, would demand enlargement in the associated parts of the brain. Thus, as reported in “Survival of the Sniffer,” researchers examining “primitive” mammalian skulls with CT scans concluded that it wasn’t survival of the smartest but survival of the best “smellers” that drove mammalian brain evolution.

Analogously, some evolutionists speculate that enhanced visual acuity drove evolution of the bird brain. Assuming that flight requires advanced neurological wiring to optimize vision and coordination, some evolutionists have speculated that theropod dinosaurs had to evolve hyperinflated forebrains before they could evolve into birds. Mark Norell of New York’s American Museum of Natural History decided CT scans might help his team peek back into evolutionary ancestors of birds and find those transitional brains.

Impressive Brains

“What's really interesting about birds is that as their brain develops, it fills so much of the cranial cavity that it creates an impression on the surrounding bones," say Amy Balanoff, lead author of Norell’s study. “If you fill that space in and get rid of the bones, you have a cast [endocast] of what the brain looked like during life.”

The fossilized endocast of Archaeopteryx—long acknowledged as an extinct kind of bird4 and considered by many a transition between dinosaurs and birds—reveals its brain was much like that of modern birds.5 Missing is its evolutionary history.

With CT-scanning technology the team digitally reconstructed the brain anatomy of modern birds, Archaeopteryx, and several theropods. Archaeopteryx was the only extinct bird included. From these digital endocasts the team calculated total brain volume as well as the relative size of each division of the brain.

So what brains were in the sample of 26 brains Norell’s team examined? Modern birds were well-represented by brains from the major bird groups—woodpeckers, passerines, nightjars, pigeons, parrots, loons, grebes, albatrosses, pelicans, falcon, cranes, ducks, and chickens. The ostrich represented flightless birds. These birds’ brains were all similar.6

Several oviraptorosaurid skulls were scanned, and the proportional volume of each section of their brains were all similar to each other and a little different from the other animals tested. Several troodontid dinosaurs bearing little similarity to each other were included, and their brain proportions differed from birds and from each other. The brain proportions of dinosaurs like T. rex were statistically the most un-birdlike of all.7

Transitioning To Take-Off

By lining up the volume calculations, the researchers believe they have reconstructed the evolutionary history of bird brains. They note that the volume of the Archaeopteryx brain is intermediate between modern birds and basal theropods like tyrannosaurs.8 Because some of the oviraptorosaurs and troodontid dinosaurs had fairly large brain volumes relative to their size—even larger than Archaeopteryx—but not as large as modern birds, the researchers propose that a number of dinosaurs evolved flight-ready brains before any made the evolutionary leap to the skies.

Norell’s team suggests that Archaeopteryx is not as unique a transitional creature as previously thought. They write, “If Archaeopteryx has a ‘flight-ready’ brain, which is almost certainly the case given its postcranial morphology [the rest of its body], then so did other paravians.”9 (Paravians are modern birds as well as all the dinosaurs supposed to have been in their ancestral lineage.)

“Archaeopteryx has always been held up as a transitional species between nonavian dinosaurs and birds, but our study shows Archaeopteryx isn't unique in being in that space between more primitive dinosaurs and birds,” says Balanoff. “We found all these other closely related species that also fall in that close transitional space.”

Bird Essentials

Though a few of the species examined had more brain volume than Archaeopteryx, Archaeopteryx did have a uniquely birdy-brained feature called a wulst. The wulst is a cerebral indentation important for information processing and muscle control. The other extinct creatures in the study did not have a wulst. The wulst is “not necessarily necessary” for flight, Balanoff explains, but “it is helpful. So maybe Archaeopteryx is not special, but maybe there is a character that it shares with living birds that isn't found in some other non-avian dinosaurs.”10

Balanoff and colleagues wrote of their hypotheses concerning some “dinosaurs” that clearly had real feathers and wings and which we would unquestionably consider to be birds—such as the four-winged Anchiornis.11 However, none of these were actually included in their sample. Perhaps CT imaging of these birds-not-called-birds would reveal birdbrain features such as a wulst. The focus of the study, however, was not to investigate the brain structure of flying creatures but to invent an evolutionary story with a transitional flight-ready dinosaur brain in the starring role.

No evolutionary change from one kind of animal into another has ever been observed either in living creatures or in the fossil record. Therefore, the evolutionary history the researchers come up with for the brain parameters they’re trying to track is subject to interpretation. They admit, “The evolutionary history of those volumetric expansions that makes the endocranial space of modern birds so distinctive depends largely on how we interpret Archaeopteryx.”12 Norell’s team admits they might learn more about the cerebral requirements for flight if they were to sample “a wider range of bird-like, non-avian theropods”13 since “avialans are not unique among maniraptorans in their ability to fly in some form.”14

Queue Up and Connect the Dots

Variations in brain size, however, do not demonstrate that animals were evolving bigger brains.

Regardless of the order in which the researchers arrange the animals, they are certain that big brains evolved. “The story of brain size is more than its relationship to body size,” says coauthor Gabriel Bever. “If we also consider how the different regions of the brain changed relative to each other, we can gain insight into what factors drove brain evolution as well as what developmental mechanisms facilitated those changes.”

“For a long time, bird brains were considered really different than those in other so-called reptiles,” explains Norell. “This is another case where the attributes that we traditionally have associated with birds actually can be seen cascading down the tree of life. We can now say that the bird brain was present in animals that were not really birds.”

Variations in brain size, however, do not demonstrate that animals were evolving bigger brains. And variations in the proportion of the brain devoted to more cognitive functions do not demonstrate that animals were evolving into smarter kinds of animals. These differences are merely differences. Nothing about them shows that the animals possessing them can be lined up in order of their measurements to show that they evolved into one another or the order in which they did so.

Biological research has not demonstrated any instance or mechanism by which one kind of animal can acquire the genetic information to evolve into a new and more complex kind of animal. Instead, animals vary only within their created kinds, and this observation is consistent with their biblically described creation. According to Genesis chapter one, God created all kinds of creatures to reproduce after their kinds.

Designed To Do What They Do

It is no surprise to learn that some kinds of dinosaurs had brains with greater volume or different regional proportions than others. Flying might require a distinctive cerebral structure, but this study did not address that. Yet flight is not the only purpose for an animal’s “advanced” brain. Oxford University zoologist Adrian Thomas comments that compared to walking and running, the “processing power required for flight is relatively simple,” adding, “So it is interesting, but not a great surprise, to see increased brain size in these dinosaurs associated with their highly agile lifestyles.”15.

Being equipped to walk, run, or fly is no indication of evolution. God created all kinds of animals fully able to function in the world. As the common Designer of all, He provided each with brainpower or other abilities to deal with the life for which He designed them. Mammals and birds did not have to evolve big brains but only to use the ones God gave them.

Furthermore, Archaeopteryx is just an extinct bird with some unusual features. That its brain is similar but not identical to those of living birds is consistent with its design by the Designer of all birds. God created all kinds of birds on the same day, so Archaeopteryx neither evolved from dinosaurs nor into modern birds.

Likewise, the discovery that some sorts of dinosaurs had brain proportions that differed from others does not demonstrate evolutionary progression but simply God’s particular design for them. Evolutionary imagination demands a naturalistic progression from one kind of animal to another, but the observable facts of biology—in which animals vary and reproduce only within their kinds—are consistent with the biblical history of life.