Horizon Season 1981 Episode 12 Did Darwin Get It Wrong?

In the sixth episode of the twelfth season of the BBC documentary series Horizon, titled "Did Darwin Get It Wrong?", the show investigates the emerging field of evolutionary developmental biology, or evo-devo, and explores whether this new scientific understanding of genetics, cellular biology, and embryology can challenge and revise Charles Darwin's classic theory of evolution by natural selection.

The episode begins by introducing the audience to two of the leading researchers in evo-devo: Sean Carroll, a biologist at the University of Wisconsin-Madison, and Neil Shubin, a paleontologist at the University of Chicago. They explain that recent discoveries in genetics and molecular biology have shown that the development of an organism from a fertilized egg to a full-grown adult is much more complex and nuanced than Darwin and his contemporaries could have ever imagined. Rather than simply being shaped by genetic mutations and natural selection, an organism's development is influenced by a wide range of factors, including gene expression, regulatory networks, and environmental signals.

The show then delves into some of the specific ways that evo-devo is challenging and expanding Darwin's ideas. For example, Carroll and his colleagues have found that the same basic set of genes and regulatory pathways control the development of body structures like wings or jaws in a wide range of animals, from fruit flies to humans. This suggests that the same mechanisms that drove the evolution of these structures in different lineages may have been present in their common ancestors, which in turn could help explain why certain traits have evolved convergently in different species.

Meanwhile, Shubin and his team have been studying a key transitional fossil discovered in the Canadian Arctic: Tiktaalik, a fish-like creature that lived around 375 million years ago and had a number of features that are intermediate between fish and tetrapods (four-limbed animals). By studying the development of modern fish and tetrapods, as well as the genes and developmental pathways that control limb formation in these groups, Shubin and his colleagues have been able to reconstruct the likely evolutionary steps that led to the emergence of tetrapods from fish.

Throughout the episode, the show presents a nuanced and balanced view of the relationship between evo-devo and Darwinian evolution. While the researchers featured in the episode are clearly excited about the potential of evo-devo to shed new light on the mechanisms of evolution, they are careful to emphasize that their work is not intended to overthrow Darwin's theory, but rather to build upon it and refine it in light of new evidence and insights.

The episode also features a number of fascinating examples of the ways in which evo-devo is shaping our understanding of the natural world. For example, the show explores the bizarre and intricate mating rituals of the Australian bowerbird, which involves the construction of elaborate decorated nests, and how the development of the bird's brain and behavior may be shaped by the same genes and networks that control limb formation in other animals. The episode also looks at the evolution of the human brain, and how a better understanding of the developmental pathways that led to its growth and complexity can shed light on the emergence of human cognition and consciousness.

Overall, "Did Darwin Get It Wrong?" is a fascinating and thought-provoking exploration of a rapidly expanding field of scientific research, and a testament to the ongoing relevance and adaptability of Darwin's ideas about evolution. Whether you are a seasoned science enthusiast or simply curious about the natural world, this episode is sure to provide new insights and inspire further reflection on one of the most profound and enduring questions in human history: where did we come from?