Teeth are an essential part of the animal kingdom, but have you ever wondered how they first evolved? A recent study on animal fossils suggests that teeth initially served as sensory organs rather than tools for chewing. The earliest tooth-like structures were actually sensitive nodules on the skin of early fish, which could detect changes in the surrounding water.
This groundbreaking finding sheds light on the evolutionary history of teeth and supports the idea that teeth first emerged outside the mouth. Yara Haridy, a researcher at the University of Chicago, explains that while there was some evidence to support this theory, the question of the purpose of external teeth remained. One possibility was that they acted as defensive armor, but Haridy believes that these structures also served a sensory function, helping organisms sense their environment.
True teeth are unique to backboned vertebrates like fish and mammals. While some invertebrates have tooth-like structures, the underlying tissues are fundamentally different. This indicates that teeth originated during the evolution of the earliest vertebrates, specifically fish.
Haridy and her team conducted a detailed analysis of fossils claimed to be the oldest examples of fish teeth. Using a synchrotron scanner, they examined fragmentary fossils of animals called Anatolepis, which had a hard exoskeleton with tubules. Previous interpretations suggested that these tubules were dentine precursors, leading to the conclusion that Anatolepis was an early fish.
However, the research team discovered that the internal anatomy of these tubules resembled sensilla found on the exoskeletons of arthropods like insects and spiders. Sensilla are sensory structures that detect various stimuli such as taste, vibration, and changes in air currents. This revelation indicates that Anatolepis is an arthropod, not a fish, and its tubules are not direct precursors to teeth.
Gareth Fraser, a researcher at the University of Florida, notes that while dentine is a vertebrate novelty, the sensory capabilities of hardened external surfaces were present in invertebrates much earlier. The team identified Eriptychius as the oldest known example of true teeth, which were present in the Ordovician Period. These teeth, located in odontodes on the skin, had sensory functions.
The study suggests that invertebrates like Anatolepis and early vertebrates like Eriptychius independently evolved hard, sensory nodules on their skin to navigate ancient seas. Modern fish still have sensory nerves in the odontodes on their skin, indicating a sensory function. As some fish transitioned into active predators, these hard structures eventually made their way into the mouth for biting.
In conclusion, tooth-like structures likely first evolved on the skin of early vertebrates before transitioning into oral structures known as teeth. This research provides valuable insights into the evolutionary history of teeth and highlights the sensory origins of these vital structures. As we approach the end of the year, it is important to take stock of all that has happened in the past twelve months. From global events to personal achievements, 2021 has been a year of highs and lows, challenges and triumphs. In this article, we will reflect on some of the key moments of 2021 and look ahead to what the future may hold.
One of the biggest events of 2021 was the ongoing COVID-19 pandemic. While vaccines have brought hope and progress in combating the virus, new variants and surges have continued to pose challenges. The pandemic has reshaped the way we live and work, with remote work becoming more common and virtual events replacing in-person gatherings. As we head into 2022, it will be crucial to continue to prioritize public health and safety measures to protect ourselves and our communities.
In terms of global politics, 2021 saw a number of significant developments. The United States inaugurated Joe Biden as its 46th president, marking a shift in leadership and priorities. Around the world, countries grappled with issues ranging from climate change to human rights abuses, highlighting the need for international cooperation and diplomacy. As we look ahead to 2022, it will be important to continue to work towards a more just and sustainable world for all.
On a personal level, 2021 has been a year of growth and resilience for many. Despite the challenges of the pandemic, people have found ways to adapt and thrive, whether through learning new skills, starting new hobbies, or reconnecting with loved ones. As we reflect on the past year, it is important to celebrate our successes and learn from our setbacks, using them as fuel to propel us forward in the new year.
Looking ahead to 2022, there is hope and optimism for the future. With vaccines becoming more widely available and new treatments on the horizon, we are better equipped to face the challenges that lie ahead. As we set our intentions for the new year, let us remember the lessons of 2021 and carry them with us as we move forward with courage and determination.
In conclusion, 2021 has been a year of growth, change, and resilience. As we look back on the past twelve months, let us celebrate our successes, learn from our failures, and look ahead to the future with hope and optimism. May 2022 bring peace, prosperity, and joy to all.
