Who proposed that birds are descendants of dinosaurs?

The idea that birds are descendants of dinosaurs was first proposed by Hussein, a staunch defender of evolution known as "Darwin's hound" more than 100 years ago.

Hussein was born in England in 1825. Due to his poor family background, he only received two years of formal education between the ages of 8 and 10. He became a scientist almost entirely through hard self-study. He traveled by ship to many places abroad for a long time, developing his talents during his travels and becoming a naturalist. His work was extremely amazing. He wrote more than 150 research papers in his lifetime, covering a wide range of fields such as zoology, paleontology, geology, anthropology and botany. He also compiled 10 scientific textbooks and collections of papers, and published many controversial articles on education, religion and ethics.

In a special popular lecture of the Royal Society in 1868, in order to illustrate some paleontological problems of the theory of design evolution, Huxley expounded his view: if all animals come from the same ancestor, then there must be a large gap between such classes as fish and reptiles, reptiles and mammals. He explained that there must have been some links that filled these gaps, but because they became extinct, they are no longer found in modern organisms. However, some paleontological fossils can fill the gaps. For example, there seems to be a large gap between reptiles and birds, but the Archaeopteryx found in Solnhofen, Bavaria, Germany, is indeed a half-reptile, half-bird that lived in the Jurassic period: it had feathers, but also teeth, long tail vertebrae and fingers. Since birds jump and walk on their hind limbs, and the two hind limbs of the upright Iguanodon known at the time and its homologous animals were "amazingly similar" to birds, this provided Huxley with the first clue to the ancestors of birds. The small Pseudopalatus, which lived with Archaeopteryx in the Bavarian slate deposits, was only about 150 cm long, with long and thin hind legs. Its appearance, size and shape were closer to those of early birds, so it was naturally considered to be related to birds.

Huxley also discussed the issue of "bird" footprints found in the Triassic New Red Sandstone Layer in Connecticut and Massachusetts, USA. Those footprint fossils were found in a section of the cut valley of the Connecticut River. They were left by some large and small three-toed and four-toed bipedal animals. Many scholars at the time believed that they were footprints of various birds. The earliest discoverer Hitchcock named them "bird print stones".

Huxley believed that the smaller footprints were left by birds, but many relics (especially the huge three-toed prints) were dinosaur footprints. Moreover, it is precisely because people can easily confuse the footprints of these birds with those of bipedal dinosaurs that the similarities between birds and dinosaurs are more prominent.

Now we know that all those footprints were left by reptiles and amphibians in ancient times, when birds had not yet appeared. But in terms of the level of human knowledge at the time, Huxley was able to infer that birds and dinosaurs were related from these footprints, which was a major achievement in his leading paleontology to support the theory of evolution.

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