The KPg boundary Chicxulub impact-extinction hypothesis: The winding road towards a solid theory

ABSTRACT

Along with the origin of life, the quest for the ultimate cause of the end of the dinosaurs and ~72% of other species is one of the most publicized questions in the history of our planet. So, it probably should not have come as a surprise that when Walter Alvarez and his team launched the impact-extinction theory, the opposition and the resistance against the theory was strong from the beginning and continues up to the present day. This paper follows the winding road around the roadblocks that were set up against the theory and how both the opposition against and accumulation of new data, e.g., the finding of the Chicxulub impact structure and extraterrestrial Cr isotope ratios to further develop the theory, went hand in hand. Often the roadblocks were overcome, but new ones were set up, and in the struggle to surmount these, the proponents were forced to look back on their arguments, to carefully re-formulate their viewpoints, and to check whether tunnel-vision had developed that might prevent seeing the data available in a different light. However, looking back on the competition among proponents and opponents 40 years later, the impact-extinction theory is stronger than ever before. It has survived and matured from a hypothesis into a well-established theory, although many questions remain to be solved.