People are always surprised to learn that I have never seen Jurassic Park (or any of its sequels), and I probably won’t see Jurassic World, either. That doesn’t keep folks from asking me if scientists will ever be able to resurrect dinosaurs. Fortunately, I can answer that question without seeing a blockbuster movie.
It’s unlikely we will ever be able to resurrect a dinosaur from ancient DNA. DNA can’t be recovered from insects trapped in amber, and it’s not stable enough to survive in dinosaur remains. Even with access to a complete dinosaur genome, scientists would face insurmountable technical hurdles if they tried to convert the genome into a living, breathing creature. (For a detailed discussion of some of those difficulties, check out this podcast.)
Still, some researchers—such as legendary paleontologist Jack Horner—think we might be able to recreate dinosaurs by manipulating the developmental process of chickens (and other birds) to turn them into dinosaur-like creatures.
Researchers from Harvard and Yale have moved the scientific community one step closer to creating a “chickenosaurus” by genetically engineering chickens to develop snout-like structures, instead of beaks, just like dinosaurs.1 For biologists, the significance of this work has little to do with the prospects of bringing dinosaurs back to life, but instead helps them understand how beaks emerged as an evolutionary innovation.
Paleontologists argue that shared anatomical features between birds and dinosaurs (classed as theropods) demonstrate a shared evolutionary history. So, too, do feathered dinosaurs. Work like this latest venture reinforces the notion that birds descended from dinosaurs by seemingly providing insights into the types of molecular and developmental changes responsible for bird evolution.
The Harvard-Yale work also serves as a harbinger of “reverse evolution,” a new approach to paleontology.2 The idea is to gain understanding of how biological transformations took place by reverting organisms to their ancestral state. Reverse evolution experiments fuse insights from paleontology with those from developmental biology, molecular biology, comparative embryology, and genomics. For the first time, researchers can address questions in evolutionary biology using an experimental strategy.
The Harvard-Yale investigators chose to study the origin of beaks because beaks are a defining feature of modern birds and a key biological innovation in life’s history. Beaks’ diverse functions allow birds to exploit a wide range of ecological niches.
Reversing the Evolution of Beaks
Paleontologists compared the skeletal anatomy of modern birds with ancient birds (such as Archaeopteryx) and theropod dinosaurs, concluding that the beak evolved when facial bones called the premaxilla fused and elongated. They also compared chicken and emu facial development with what occurs for alligators, turtles, and lizards. This comparison convinced them that dinosaur facial development was similar to that of today’s reptiles.
During development, cells produced two proteins—the growth factors dubbed Fgf8 and Lef1—in a large region of the chicken embryo’s face, but only in small patches in the reptile embryo’s face. Based on these insights, the researchers reasoned that changes in the expression of genes that encode these growth factors likely played a key role in snout-to-beak evolution. To test this idea, they implanted microscopic beads coated with chemicals that inhibit Fgf8 and Lef1 into the facial region of chicken embryos. The chicken embryos retained beaks externally, but the disruption in the growth factors led to snout-like internal skeletal structures similar to modern-day reptiles, theropods, and ancient birds.
The researchers still don’t know what specific genetic changes led to altered gene expression of the growth factors, nor do they believe they have provided the complete explanation for beaks evolution from snouts. But they do believe they have gained important insight into key changes that contributed to bird evolution and have demonstrated the power of reverse evolution as a strategy to understand life history from an evolutionary framework.
A Creation Model Approach to Bird Origins
Though this work and the case for bird evolution seem compelling, the reverse engineering studies’ results and the observations from the fossil record can be readily explained from a creation model perspective.3 Key to this explanation is the work of Sir Richard Owen, a preeminent biologist who preceded Darwin. In contemporary biology, scientists view shared features possessed by related organisms as evidence of common ancestry, but for Owen, shared anatomical features reflected an archetypical design that originated in the Mind of the First Cause. Therefore, the anatomical features shared by birds and theropods can be understood as reflecting common design, as opposed to common descent.
Though Owen’s ideas were sound, they were largely abandoned in favor of Darwin’s theory because many biologists preferred a mechanistic explanation for life’s history and the origin of biological systems. In fact, one could argue that Darwin’s theory is an adaptation of Owen’s archetype, replacing the canonical blueprint of the Creator’s Mind with a hypothetical common ancestor.
This archetypical approach to biology can account for the results of reverse evolution studies, such as converting a bird’s beak into a dinosaur snout. Accordingly, the researchers merely stumbled upon differences in the developmental program (production of the growth factors Fgf8 and Lef1) that affect variations in the archetype, yielding beaks in modern birds and snouts in modern reptiles, ancient birds, and dinosaurs.
From the standpoint of genetics, it’s possible the Creator selected a gene set that can be used to construct a wide range of organisms, organized around a single archetype, simply by varying gene expression. Think of an organism’s set of genes like a set of building blocks. Depending on the builder’s imagination, he or she can create a variety of structures with the same set of blocks. Likewise, a Creator could produce different organisms by deploying the same set of genes in different ways.
This is a common design principle. From a creation model standpoint, the Harvard-Yale researchers didn’t reverse the evolutionary process. They unwittingly reverse engineered a snout from a beak based on design principles.
Adding further credibility to a creation interpretation is the amount of knowledge and insight into the developmental process that was required to carry out these (and other) reverse evolution experiments. Equally impressive was the care required to alter the influence of the two growth factors. To transform a beak into a snout required coordinated, coherent, and precisely localized changes in growth factor levels. The researchers intelligently designed the conversion of the chicken’s beak into snout-like structures. So, is it reasonable to think that unguided, historically contingent processes could carry out such transformations when such small changes can have such profound effects on an organism’s anatomy? Because evolutionary mechanisms can only change gene expression patterns in a random, haphazard manner, the best such processes could achieve would be the generation of “monsters” with little hope of survival.
I would contend that the coherent, precisely coordinated genetic changes needed to generate one biological system from another bespeaks of the Creator’s handiwork as the explanation for life’s history.
- Bhart-Anjan S. Bhullar et al., “A Molecular Mechanism for the Origin of a Key Evolutionary Innovation, the Bird Beak and Palate, Revealed by an Integrative Approach to Major Transitions in Vertebrate History,” Evolution (2015), doi: 10.1111/evo.12684.
- Carl Zimmer, “Reverse Engineering Birds’ Beaks into Dinosaur Bones,” New York Times, posted May 12, 2015, https://www.nytimes.com/2015/05/12/science/reverse-engineering-birds-beaks-into-dinosaur-bones.html.
- It’s important to recognize that the feathered dinosaurs—interpreted as transitional intermediates—appear in the fossil record after the first bird appears. Paleontologists refer to this as the temporal paradox. The out-of-sequence fossil record justifies skepticism about the evolutionary explanation for bird origins.