Conventional scientists have been baffled for many years by the small arms of Tyrannosaurus rex. To many, they just seem disproportionately small compared to other theropod dinosaur arms. The question is often asked: What use could these tiny arms be for such a large predator? A recent study claims to have solved this enduring enigma.¹ And yet, a simple visit to a playground teeter-totter would have likely saved them a lot of time and effort.

Charlie Scherer, a Ph.D. student at University College London, and his colleagues examined the head dimensions and arm size of 85 theropod species (meat-eating dinosaurs).¹ Skull-to-forelimb ratios were calculated for 61 of the 85 species. They also developed a new cranial robusticity score that included skull proportions, bite force, and dental morphology.¹ Cranial robusticity—including components like bone thickness, size and shape of the skull, and teeth—helps researchers understand differences in how and what a dinosaur might have eaten.

It also may help explain T. rex’s little arms. The study’s results demonstrated a direct relationship between cranial robusticity and arm size, suggesting that the arms are small because they didn’t play as significant of a role in T. rex’s eating style.¹ But dinosaur behavior is difficult to assess from bones alone. Nonetheless, the conventional team of paleontologists tried to tie the relative skull and arm size relationship to an unknown evolutionary process: “Results indicate that forelimb reduction is strongly correlated with cranial robusticity and gigantism. Reduced/vestigial forelimbs evolved in at least five theropod lineages in concert with increased cranial robusticity and gigantism.”¹ So the authors believe that random evolution caused the arms to became smaller over time, even referring to them as vestigial.

Scherer added, “We sought to understand what was driving this change and found a strong relationship between short arms and large, powerfully built heads. The head took over from the arms as the method of attack.”²

They further attempted to connect the cranial robusticity to the general diet of the theropod:

Therefore, it is highly likely that a predator’s cranial robusticity was linked to the characteristics of the organisms it was preying upon. Larger prey items would have required a larger, more robust skull to resist the inevitably higher forces experienced when attacking/restraining heavier prey.¹

Ultimately, the conventional scientists concluded that the larger body size of prey required larger skulls and a larger cranial capacity at the expense of arm size.¹ Scherer said,

While our study identifies correlations and so cannot establish cause and effect, it is highly likely that strongly built skulls came before shorter forelimbs. It would not make evolutionary sense for it to occur the other way round, and for these predators to give up their attack mechanism without having a back-up.²

But does this evolutionary tale make sense? How could a larger head evolve first and then the arms somehow become smaller over vast amounts of time? Maybe there is a better explanation for this head and arm size relationship—one that points to a perfectly balanced design.

Bipedal (two-footed) dinosaurs, like theropods, balanced at their back hips. The tail balanced the head, arms, and upper torso. The engineering has to be just right to keep the weight distributed equally. Just like a teeter-totter has to balance with the same weight on either end for best performance, so did the bipedal dinosaurs. A larger head combined with large forelimbs would throw the balance off, making the dinosaur overly front-loaded. It would walk awkwardly out of balance, to say the least. To counterbalance that, the tail would have to grow even bigger.

Recognizing such engineering behind the skull and arm size relationship harkens back to the Creator and creation week rather than random mutations and deep time. The Lord Jesus engineered all animals to be perfect in all their dimensions, from the front of the skull to the tip of the tail. Head size was most likely based on what plant types each dinosaur was designed to eat. If they needed a large skull to eat large plants, then their arms would have been designed smaller to accommodate that. It’s also likely that larger-headed dinosaurs with small arms didn’t use their arms to feed.

In the end, it’s all about engineering and balance. Theropod dinosaurs never slowly evolved longer arms or shorter arms. The arms were always in perfect proportion to their skulls and their tails, no evolution required. And because the Lord always has a purpose, we can trust the small arms of the T. rex had a purpose, too, even if we don’t yet know exactly what that purpose might have been.

References

1. Scherer, C. R., E. Steell, and P. Upchurch. 2026. Drivers and Mechanisms of Convergent Forelimb Reduction in Non-Avian Theropod Dinosaurs. Proceedings of the Royal Society B. 293 (2071): 20260528.
2. University College London. T. rex’s Tiny Arms May Have Evolved for a Surprisingly Brutal Reason. ScienceDaily. Posted on sciencedaily.com May 20, 2026, accessed June 2, 2026.

* Dr. Clarey is the director of research at the Institute for Creation Research and earned his doctorate in geology from Western Michigan University.