Solution to the Paradox of Terrestrial Gigantism during the Mesozoic Era

The paradox of how the dinosaurs and pterosaurs grew so large has existed for over two centuries, and during this time paleontologists and others have proposed numerous hypotheses. This first section, “Where Did the Paleontologists and Others Go Wrong?” explains the problems with those hypotheses. If you are in a hurry to check your answer to how the dinosaurs and pterosaurs grew so large, you can skip ahead to the next section titled “Finding Solutions by Applying Science and Imagination”.

Where Did the Paleontologists and Others Go Wrong?

When Ernest Rutherford said, “All science is either physics or stamp collecting,” he was likely thinking about paleontology: the hobby scientists who spend little time studying core sciences like physics before pursuing their interest in collecting dinosaur bones and other fossils. Consequently, it is not surprising that paleontologists have sometimes misunderstood the laws of nature, including uniformitarianism. These gaps in understanding have contributed to their longstanding difficulty in explaining how Mesozoic animals grew so large.

Uniformitarianism is the principle that the laws of nature - those described by physics and chemistry - are constant and operate uniformly across the universe and throughout all of time. Geology, astronomy, and other sciences build on this foundation, while often not emphasizing enough that uniformitarianism itself refers to the invariance of natural laws, not to the stability of environments or conditions.

Geology instructors typically explain uniformitarianism by stating, “The present is the key to the past.” This phrase helps geology and paleontology students understand that the way to make sense of rock and fossil evidence is to observe present-day geological activity and then imagine these same processes taking place millions of years ago. However, this phrase is not precisely what uniformitarianism means. Again, uniformitarianism means that the core laws of science - think physics and chemistry - are applicable throughout time and space. The subtle difference between what uniformitarianism actually means and how it is explained has led geology and paleontology students to incorrectly believe that the past should resemble the present.

Because of this misinterpretation, the paleontology community believed that they should not consider the possibility of the Mesozoic environment being dramatically different from the present environment. This mistake guarantees that they can never find the answer to the paradox of the gigantic animals of the Mesozoic era. Looking elsewhere for the answer, they have spent the past two centuries proposing questionable ad hoc ‘solutions’ for the problems associated with oversized animals. Typically these ‘solutions’ are claims that dinosaurs and pterosaurs were in one way or another biologically superior - lighter and stronger bones and muscles and so on - than modern species. Eventually other scientists point out what is wrong with their claim, and then the pattern repeats. This has produced a record of failure that has harmed not only the credibility of paleontologists but also the credibility of science in general.

It is this long record of failure that has encouraged many people outside paleontology to attempt to solve the problem. As one might expect, most of these proposals - especially those from individuals without scientific training - end up violating the laws of nature in one way or another.

One of the better, though still incorrect, proposals is the suggestion that the universal gravitational constant may have changed over time, thus weakening Earth’s gravitational field and allowing larger terrestrial animals to exist. This proposal is wrong because it violates the principle of uniformitarianism. Like the fundamental belief of science - that we exist in a rational reality - there is no formal proof that uniformitarianism is true. Instead, what we have is an overwhelming body of interconnected evidence supporting the belief that the laws of nature are consistent across time and space. Making an exception to uniformitarianism just to account for large dinosaurs would create infinitely more problems than it would solve.

A more fringe idea is the so-called expanding Earth hypothesis - an outdated attempt to explain why the continents on either side of the Atlantic fit together like puzzle pieces. It was once taken seriously but fell out of favor after the discovery that seafloor spreading at the Mid-Atlantic Ridge was creating the Atlantic Ocean. With overwhelming evidence supporting the Theory of Plate Tectonics, no scientist today questions its explanation of continental movement. Proponents of the expanding Earth idea are like the flat-Earth believers in refusing to accept the strong evidence indicating that they are wrong. Most damning is the fact that they have failed to provide a plausible mechanism for how the planet could expand. Some now claim that expansion also explains the size of dinosaurs, but this also makes no sense: if we apply the gravity equation, a smaller, compacted Earth would have a stronger gravitational field, meaning Mesozoic animals would actually be smaller - not larger - than today’s land animals.

While the paleontology community has mostly shunned environmental solutions to address the paradox of gigantic Mesozoic animals, there have been a couple of exceptions where proposals were made which, while they may appear to solve one specific problem, failed to account for all of the gigantic animals of the Mesozoic era.

The oxygen-rich atmosphere hypothesis proposes that higher O₂ levels in the past would have improved respiration and supported higher metabolic rates, making it easier for animals to sustain energy-demanding activities such as flight. This argument has been used to suggest that giant pterosaurs, and to some extent large dinosaurs, could have functioned more effectively in such an environment. However, while greater oxygen may boost metabolism, it does not reduce the structural stresses imposed by large body size - bones and muscles would still face the same mechanical limits. In addition, oxygen concentrations cannot be excessively high without creating uncontrollable wildfire conditions, and the fossil charcoal record shows that atmospheric oxygen during much of the Mesozoic was actually lower than today, often in the range of 15–18%. These findings undercut the idea that higher oxygen explains the gigantism of dinosaurs or the flight of enormous pterosaurs.

To explain how massive dinosaurs such as Brontosaurus (now Apatosaurus) could support their weight, early paleontologists proposed that sauropods lived like hippos, spending most of their time partially submerged in lakes or swamps so that buoyancy could offset their bulk. This view persisted for decades until closer study of their skeletons revealed that their limbs and feet were unsuited to an aquatic lifestyle. Once sauropods were “brought onto land,” paleontologists relied on ad hoc claims - such as unusually light bones or extensive internal air sacs - to sidestep the weight problem. In 2012, however, British biologist Brian J. Ford reignited controversy by arguing that all dinosaurs required water to support their mass, claiming their legs were too weak for a fully terrestrial life and their body shapes better suited to an aquatic environment. While Ford raised valid concerns that paleontologists often avoid, he himself overlooked problems such as the abundance of dinosaur trackways, dinosaur’s structural anatomy giving evidence of their terrestrial adaptations, the respiratory limits of an aquatic existence, and the unanswered question of how giant pterosaurs and enormous birds could have achieved flight.

Finding Solutions By Applying Science and Imagination

Real science begins with imagination - the kind that challenges assumptions, sparks new questions, and works within the laws of nature. To know the extent or limits of what is possible, one must first have a thorough understanding of those laws.

The size of animals is limited by the materials of their bodies and the environment in which they live. Gravity multiplied by mass determines weight, and to support this weight, terrestrial animals must have muscles strong enough to lift their bodies off the ground and bones strong enough to withstand both the load and any sudden jolts or falls. If bones break under stress, survival is unlikely. Since weight depends on gravity, a weaker gravitational field would allow animals to grow larger.

To better understand how a planet’s gravitational field can affect the size of animals let’s imagine traveling to other worlds. For simplicity’s sake, science fiction writers usually ignore how different gravity would affect their characters: they beam down to alien worlds and walk about as if the gravity were identical to Earth’s, even though that is unlikely. In reality, when astronauts walked on the Moon, they did not move normally but used a light, bouncing hop because gravity there is only one-sixth that of Earth’s. If humans were to colonize the Moon or Mars, then generations later the reduced stress on muscles and bones in the weaker gravity would likely allow colonists to grow larger than Earth-born humans.

But how could Earth itself, with its gravitational field being constant, allow dinosaurs of the past to grow so much larger than the terrestrial animals of today? One way of decreasing the effective weight of animals - and thus enabling them to grow larger - is through the buoyant force of fluids. Whales, for example, are the largest animals alive today because the buoyancy of water effectively reduces their weight to zero. In an attempt to explain how some dinosaurs could be so large, paleontologists first suggested that sauropods waded partially submerged in water, but they eventually abandoned this idea. Likewise, Brian J. Ford’s proposal that they were fully submerged is also incorrect: if dinosaurs had lived entirely underwater, then like whales, they would have lost their legs because they would have had no further need for them.

To find the answer, consider Venus. While it is nearly the same size as Earth, its surface gravity is 91% of Earth’s, and its atmosphere is 91 times denser. That density provides buoyancy, reducing the effective weight of objects on its surface. A person standing on Venus would weigh about 9% less due to lower gravity and an additional 7% less due to atmospheric buoyancy. For example, a 180-pound person would weigh only 151 pounds on Venus. Now imagine an atmosphere hundreds of times denser than Earth’s - such an atmosphere could reduce effective weight almost as much as water does.

The answer should now be obvious: Earth must have had an extremely thick atmosphere during the Mesozoic era. An atmosphere hundreds of times thicker than today’s could account for the enormous dinosaurs, flying pterosaurs, and the other paradoxical features of that era. And yet, before accepting this conclusion, we should check whether such a thick atmosphere was possible.

Many people, accustomed to today’s thin air, wonder how Earth’s atmosphere could ever have been hundreds of times thicker. But in fact, there is no physical limit to atmospheric thickness. Within our own solar system, Jupiter and the other three gas giant planets likely consist of a relatively small rocky core surrounded by an atmosphere tens of thousands of times thicker than Earth’s. Scientists already know that Earth’s atmosphere has changed dramatically in composition over billions of years, so there is no reason to assume its thickness could not also have varied dramatically.

Another question is whether the extreme pressure of such an atmosphere would have made life impossible. The answer is no. An atmosphere hundreds of times thicker than today’s would create pressures at Earth’s surface comparable to those at the bottom of today’s oceans. Countless deep-ocean creatures thrive under such conditions without difficulty. Likewise, dinosaurs would not have been harmed by, or even noticed, the high pressure of their environment.

Once one accepts the possibility of a much thicker atmosphere, the paradox of giant Mesozoic animals disappears. A review of the so-called paradoxes listed in the introduction reveals that they are not paradoxes at all, but compelling evidence that Earth had a much thicker atmosphere during the Mesozoic era.

The Thick Atmosphere Solution is like the Theory of Evolution: they are both scientific breakthroughs that greatly advance our understanding of reality. Both are supported by an exceptional number of independent, evidence-based arguments. Yet both have faced resistance: the Theory of Evolution from religious groups unwilling to give up claims of a divine soul, and the Thick Atmosphere Solution from paleontologists who have misled the public to avoid admitting they are wrong. Neither theory should be treated as controversial.

Revolutionary Science

DinosaurTheory goes far beyond explaining how dinosaurs grew so large, how the giant pterosaurs flew, or why there was no ice at the Polar Regions during the Mesozoic era. DinosaurTheory explores how planets evolve over time - particularly how Earth’s atmospheric evolution has shaped, and been shaped by, the evolution of life. It explains where Earth’s thick atmosphere came from - and where it went. DinosaurTheory reveals why Earth’s current atmosphere is so different from those of the other planets.

DinosaurTheory is a broad, evidence-based theory that integrates multiple scientific disciplines. Readers are encouraged to reread sections and check references to fully grasp the material, as scientific ideas - especially those that challenge the status quo - can take time to absorb. Though DinosaurTheory may read somewhat like a textbook, it introduces a wealth of new scientific insights that are both engaging and enlightening.

Many of these ideas, while revolutionary in today’s scientific climate, are rooted in conservative, well-established principles of physics and science in general. In a healthier scientific environment, they would already be part of standard science education. DinosaurTheory represents a major step forward in restoring scientific integrity and in advancing our understanding of Earth, the evolution of life on Earth, and the evolution of the planets in our solar system.

Click Here To Return to Introduction
David Esker
M.S. Physics
College Physics Instructor
Resolution of the Large Dinosaur Paradox
Science of Flight Equations
Theory of Planetary Evolution
Author of DinosaurTheory

Science is an ongoing process of discovery. We do not know why our reality exists, we struggle in defining what is life, we do not know how the laws of physics came to be, or who set the values of the physical constants, but we are certain of one thing: our reality is rational.

Comments, Questions, and Answers

Selected comments and questions are given with the permission of the parties involved.