Having undertaken some novel genetic experiments, researchers from the University of Chile are about to make an incredible discovery. The group had been tinkering with the genetic makeup of chickens, and now they’re scrutinizing an embryo which they have created. Evidently, their work has been worthwhile, as what they’re seeing lays bare the evolutionary connection between chickens and their dinosaur ancestors.
In essence, the scientists had biologically engineered chickens with the legs of a dinosaur. And to do this, they utilized “reverse evolution” techniques. The process was ultimately a success – meaning that the possibility of creating some sort of chicken-dinosaur hybrid isn’t entirely unthinkable down the line.
For fans of Steven Spielberg, this engineering process might recall memories of 1993’s Jurassic Park. After all, that classic sci-fi flick focused on the mayhem that resulted from scientists fiddling with dinosaur genes. Though clearly the experts involved in this real-life research have more of a handle on the situation than their fictional counterparts.
Of course, the work conducted in Chile shows the genetic resemblance between birds of the present and ancient dinosaurs. Yet this notion is itself far from new. For some time now, experts have been aware of this connection, and there’s evidence of it in the fossil record.
The birds we see today actually trace their beginnings back to a certain assortment of dinosaurs known as theropods. These creatures walked on two legs – each of which held three toes. Perhaps the most famous examples of theropods known to us today are the Velociraptor and the Tyrannosaurus rex.
The theropods most similar to modern birds were actually much heavier – weighing up to 500 pounds. And rather than beaks, it seems that they possessed sizable snouts within which lay large teeth. Plus, their brains were extremely small in comparison to the overall size of their skulls.
For many years, the only physical evidence of the connection between modern avians and dinosaurs was the Archaeopteryx. Fossils belonging to this ancient animal were unearthed in Germany and painted a picture of a sort of hybrid beast. Like birds, for instance, the Archaeopteryx apparently possessed wings covered in feathers. But it also had teeth and a tail like other sorts of dinosaurs.
The more bird-like characteristics of the Archaeopteryx are thought to have developed quickly – in roughly ten million years. Naturally, this seems like a long time, but in terms of evolution it represents little more than an instant. As paleontologist Michael Benton put it to Quanta Magazine in 2015, “Archaeopteryx seemed to emerge fully fledged with the characteristics of modern birds.”
By way of explaining this swift burst of evolution, a hypothesis known as “hopeful monsters” has been put forth. This infers that significant genetic alterations can quickly occur in organisms which are distinct from more regular evolutionary changes within other species. Such a process could have seen large theropods rapidly turn into a smaller ancient bird known as a Iberomesornis.
However, as more research has continued, a more nuanced history of bird evolution has been developed. In fact, more recent discoveries have suggested that certain bird characteristics showed up in dinosaurs well before birds themselves evolved. As such, it’s possible that birds adapted specific characteristics of certain dinosaurs – like feathers – for their own purposes.
More recent studies have argued that modest adjustments which occurred in dinosaurs ultimately led to birds. For example, dinosaur skulls started to change shape into something like what we see in birds today. And though they eventually became quite a bit smaller, the connection between birds and their ancient predecessors can still be noted.
By paying attention to the evolutionary history of birds, a certain idea can consequently be extrapolated. This, essentially, is that relatively subtle changes within a specific species can have massive implications on its evolutionary descendants. In the case of birds, this may explain how they picked up the capacity to fly.
In the 1990s a wave of newly uncovered fossils emerged within China. Quite a number of these ancient remains belonged to wingless dinosaurs, yet they also exhibited evidence of feathers. With that, experts were now forced to reassess their understanding of how dinosaurs became birds.
Before this point, feathers were thought to have strictly been a feature of birds. Now, though, experts concluded that feathers had existed in dinosaurs well before birds came into being. And subsequent study of these fossils has backed up the idea that bird evolution took longer than was once thought.
In 2014 paleontologist Stephen Brusatte and some colleagues published a study about coelurosaur fossils. This species was a theropod subgroup which ultimately preceded the Archaeopteryx and the birds we know today. The work of these specialists suggested that coelurosaurs didn’t become birds particularly quickly; evolutionary developments were seemingly more slight than that.
Brusatte himself explained the process to Quanta Magazine. He said, “A bird didn’t just evolve from a T. Rex overnight, but rather the classic features of birds evolved one by one. First bipedal locomotion, then feathers, then a wishbone, then more complex feathers that look like quill-pen feathers, then wings.” He added, “The end result is a relatively seamless transition between dinosaurs and birds – so much so that you can’t just draw an easy line between these two groups.”
However, as Brusatte’s research has implied, evolution moved quite quickly when birds eventually came into being as a distinct category of animal alongside other dinosaurs. This is an idea which contrasts against the hopeful monster explanation of evolutionary events. In fact, Brusatte’s ideas are almost the complete opposite of the hopeful monster theory.
According to Brusatte, birds were not the result of a sudden flash of evolution. In his mind, it was actually the other way around. He told Quanta Magazine, “It seems like birds had happened upon a very successful new body plan and new type of ecology – flying at small size – and this led to an evolutionary explosion.”
When we think of birds today, we’d likely point to their wings and feathers as being among their most distinctive features. However, we should also take note of their comparatively limited size. Birds apparently became small quite quickly – evolutionarily speaking. However, this may have happened before birds had themselves emerged as a distinct class of animal.
In 2014 research published in Science suggested that birds’ ancestors began getting smaller up to 200 million years ago. This was about 50 million years in advance of the Archaeopteryx emerging when other dinosaurs were increasing in size. As Michael Benton told Quanta Magazine, “Miniaturization is unusual – especially among dinosaurs.”
Birds’ ancestors quickly got smaller when they started to develop wings and began flying. According to Benton, their size diminished at a rate some 160 times quicker than other dinosaurs were growing. He told the online publication, “Other dinosaurs were getting bigger and uglier while this line was quietly getting smaller and smaller. We believe that marked an event of intense selection going on at that point.”
This quick rate of shrinking implies that small birds were better suited to survival than their bigger counterparts. And this may have come about as these early creatures took to living in trees. As Stephen Brusatte explained to Quanta Magazine, “Maybe this decrease was opening up new habitats, new ways of life, or even had something to do with changing physiology and growth.”
Apparently, the fact that birds’ ancestors shrunk probably helped them along the road to becoming capable of flying. This can only happen when a creature develops wings of a specific ratio compared to their own weight. So being small is a handy precondition in this regard.
Researchers working today can also look to other living creatures to learn about dinosaurs’ evolution into birds. Alligators, for example, are actually quite similar to birds – genetically speaking. With that in mind, Harvard University biologist Arkhat Abzhanov was studying alligator eggs in 2008 when he noticed that the embryos within actually resembled chickens.
And, interestingly, the fossils of young dinosaurs look quite a lot like adult birds of today. So, bearing this in mind, Abzhanov and some associates theorized that birds may have emerged as a result of dinosaurs not developing fully in the earlier stages of their lives. From there, the researchers sought to confirm their suspicions by analyzing fossils which had been discovered all over the world.
The researchers noted how similar prehistoric birds actually were to dinosaur embryos. Then, as Abzhanov explained to Quanta Magazine, “Modern birds became even more babylike and change even less from their embryonic form.” To put it simply, today’s birds are quite like how young dinosaurs had been before they developed into maturity.
The process by which birds stopped significantly developing past their embryonic states has been termed as “pedomorphosis.” Basically, this may have encouraged the shrinking sizes of ancient birds – or the exact opposite could also be true. In any case, experts believe that there is a connection between shifts in size and the course of a creature’s development.
Abzhanov is also interested in modern birds’ beaks – features that he told Quanta Magazine resemble “a pair of fingers on the face.” Indeed, beaks allow birds to undertake a variety of tasks, and so their evolution is of great interest. So, Abzhanov and some peers have conducted research on this very matter. And they’ve shown how slight alterations to a bird’s genetic makeup can turn its face into something similar to a dinosaur’s.
A bird’s beak is formed by a pair of specific bones merging together. In dinosaurs – and in modern animals such as alligators – these bones remain separate to form a snout. Abzhanov and his colleagues wanted to discover how that changed occurred, so they studied the genes associated with them in a variety of animals – including chickens, alligators, turtles and mice.
The scientists then discovered that birds had different genetic patterns expressed in their facial bones than the other creatures. So the researchers used chemicals to inhibit these genes in chicken embryos. And as a result, the developing chickens ended up forming faces which resembled those of dinosaurs.
The aforementioned experiment was, in many ways, similar to the one conducted by the researchers from the University of Chile. The scientists in Latin America, however, were focused on leg bones. You see, bird ancestors like the Archaeopteryx once had a tubular fibula bone which stretched down to their ankle. Beside this was a tibia bone of roughly the same length.
As these creatures evolved, however, the fibula shrank and the tibia ended up being larger than it. The former bone no longer joined with the ankle, and its ends were now more splintered. Amazingly, modern bird embryos exhibit legs like dinosaurs, but they ultimately change during their development. So, the University of Chile scientists decided to look into this process.
The researchers set about restricting a specific gene known as Indian Hedgehog (IHH). This meant that the chicken embryos then developed long fibulae – just as their dinosaur ancestors would have. And from this, the scientists realized that chickens are specifically impeded from developing longer dinosaur-like legs.
The experts posited that a bone found in the ankle of chickens known as the calcaneum was behind this growth restriction. They explained in a 2016 press release, “Unlike other animals, the calcaneum in bird embryos presses against the lower end of the fibula. They are so close, they have even been mistaken for a single element by some researchers.”
According to the University of Chile scientists, the relationship between a chicken’s fibula and its calcaneum leads to certain signals being given off. These ultimately block the former bone from extending and joining with the creature’s ankle. But when the IHH gene was blocked, the calcaneum itself started producing a gene known as Parathyroid-protein. This allowed the fibula to continue growing – as it would have done in bird ancestors like the Archaeopteryx.
The researchers wrote in their report, “Experimental downregulation of IHH signaling at a postmorphogenetic stage led to a tibia and fibula of equal length. The fibula is longer than in controls and fused to the fibulare – whereas the tibia is shorter and bent.”
However, the chicken embryos with these longer, dinosaur-like legs never actually hatched from their eggs. And whether or not it would be moral to allow for this is itself worthy of great consideration. In this specific study, the scientists were simply attempting to figure out how bird legs have developed over time.
The University of Chile’s Alexander Vargas told Phys.org, “The experiments are focused on single traits to test specific hypotheses. Not only do we know a great deal about bird development, but also about the dinosaur-bird transition – which is well-documented by the fossil record. This leads naturally to hypotheses on the evolution of development that can be explored in the lab.”
While this particular study is quite limited, some experts actively want to take things further. Jack Horner, for one, is a paleontology professor from Montana State University, and he wants dinosaur-like birds to actually be born. He also believes such a scenario isn’t far away, telling Live Science, “From a quantitative point of view, we’re 50 percent there.”
From Horner’s perspective, the creation of dinosaur-bird creatures would answer some important evolutionary questions. In his words, “Any of us [who] have any curiosity about how we all got here and where everything came from has to be interested in evolutionary biology. It’s basically the blueprint of life on… Earth.” But for now, it remains to be seen how far these reverse evolution experiments will be taken.