What is 20 years? For some, it is an eternity, for others a glimpse. For most students, 20 years represents the majority of theirs lives. If we assume to live for 80 years – a rather optimistic estimate – 20 years would only be a quarter of our lifetime. But how does 20 years feel to other animals? 

Let’s start with a fruit fly. This small organism is known to all of us for different reasons. Some find it annoying as it flies around our fruit bowls, reminding us of the bunch of bananas we bought on the discount and forgot to eat. To scientists, however, the fruit fly – Drosophila melanogaster – is a well-studied experimental model, used to investigate areas such as genetics and neurology. One of its key features is its short lifecycle: it takes only 10 days for an adult fly to develop from fertilized egg, and its entire lifetime averages from 30 to 40 days (Flat, 2020). What does 20 years mean to a fruit fly, then? If we do a quick calculation, 20 years is roughly 7,300 days. Dividing this by 35-day lifespan gives us about 209 lifetimes in 20 years. 

Animals living similarly long to us are whales – mammals whose way of life is quite different from ours. According to AnAge: The Animal Ageing and Longevity Database (2024), some whales are true longevity champions: the bowhead whale can live up to 211 years, the fin whale up to 114 years, and the blue whale up to 110 years. For those creatures, 20 years is less than one fifth of their lives. For the bowhead whale, it takes around 22 years to reach sexual maturity, 20 years is merely the beginning of life! 

On the other end of the longevity spectrum, we find the hexactinellid sponge, which boasts an astonishing lifespan of 15,000 years (AnAge, 2024). This makes it the longest-lived animal on Earth. Most people don’t even think of sponges as animals – they resemble strange, white tubes. Yet, they eat, grow, and live like other animals. What does 20 years mean to the hexactinellid sponge? It accounts for less than 0.14% of their entire life – a blink, nothing. Living its best life in the depths of the Ross Sea in Antarctica, far removed from disturbances, the sponge grows and exists at its own pace. 

Of course, the consciousness of animals is a completely different subject. One of the things that make humans unique is imaginative thinking – our ability to create concepts that describe and facilitate our existence. What is a year? We decided that it consists of 12 months. What is a month? A bizarre system we created, with its oddities like February sometimes having 28 days and other times 29. Other animals do not count hours, days or months. They focus on the present moment. They don’t plan a year ahead because they cannot comprehend what a year is! 

Even though animals are unaware of the concept of time, they do exist in our fast-changing world. They cannot prepare for the changes we have caused and rely solely on their instincts. They must adapt to survive. We humans have transformed the world, exposing animals to entirely new challenges. They have no knowledge of these developments or how to deal with them. Fruit flies with a lifespan of 35 days, can adapt quickly. In contrast, whales which may live for over a hounded years and are accustomed to a specific environment, face significant disruptions from these changes. A striking example of this is water pollution, including floating trash in oceans that is mistaken for food. Plastic bags, bottles, and packaging – these items didn’t exist there before, and animals often confuse them with prey. 

Some animals are particularly vulnerable. Cetaceans, like whales, which dive deep into the water, rely not on their sight but use echolocation to detect their prey. Merrill et al. (2024) demonstrated that plastic debris such as bags, ropes, and bottles acoustically mimic the prey of whales. Cetaceans generate sound waves that travel through water, bounce off objects and return to them. Whales and their ancestors have hunted this way for millennia. They cannot distinguish a plastic bag from a squid. Unaware of the mistake, they poison themselves. 

Why then has the hexactinellid sponge managed to survive over 15,000 years despite humans? Perhaps because many people don’t even know where the Ross Sea is! Hidden in the depths of these remote waters, it has remained relatively safe from human harm. However, even there, our actions leave their mark. Global temperatures are rising, leading to changes in water conditions. These shifts continue to affect even well-hidden and ancient creatures. 

Over the past 20 years, the world has changed – luckily not just for the worse. We are capable of doing amazing and seemingly impossible things. Science has progressed rapidly, giving us tools to understand and address some of the challenges. One landmark achievement in the scientific field was the Human Genome Project, completed in 2003, 21 years ago. It was an international collaboration which generated the first sequence of the human genome (Human Genome Project Fact Sheet, 2024). The project took 13 years to complete. Fast forward to March 16, 2021, when a team at Stanford University set the first Guinness World Record by sequencing the patient’s genome in just 5 hours and 2 minutes (Rahlves, 2022). That is how far we have come in less than 20 years! This remarkable leap in technology allows us to uncover all our genetic information, including predispositions to certain diseases, in mere hours. And that is just one example of our achievements. 

Returning to our fruit fry, researchers this year completed another groundbreaking project: mapping the entire brain of Drosophila melanogaster. They created a stunningly detailed map of nearly 140,000 neurons that make up its brain (Reardon, 2024). This is a significant step toward developing a similar map of the human brain and understanding the complex structure that enables us to comprehend passing years. 

Humans have changed the world in both good and bad ways. We must live with the consequences and continue to drive change responsibly. Unlike animals, we are aware of time. We are aware of our actions. We can think abstractly, plan for the future, and reflect on the past. The world is changing, and while humans can adapt voluntarily, we bear the responsibility to protect those who cannot.