Some Lakes Have Existed for Millions of Years. Can They Survive Us?

Most lakes are less than 10,000 years old and relatively short-lived. But some have endured for millions of years, surviving ice ages, volcanic eruptions, and shifting continents. These ancient lakes — including Lake Baikal in Russia, Lake Tanganyika in Africa, and Lake Ohrid in the Balkans — are not just bodies of water. They are living time capsules, preserving unique ecosystems and species found nowhere else on Earth.

Ancient lakes are biological laboratories, showcasing some of the most unusual and specialized creatures on Earth. They help us understand how life evolves in isolation, how climate has changed over millennia, and even how life might exist on other planets. Their unique biodiversity makes them biological treasure troves, helping researchers uncover the secrets of adaptation, speciation, and resilience.

So why don’t we talk about them more?

Not all lakes are alike

Just 3% of the global water is freshwater. The vast majority of that is unavailable: locked up in glaciers, polar ice caps, atmosphere, and soil, or underground. Even from the remaining part, only a minority is in freshwater lakes. Ancient lakes are yet a small part of that.

In that regard, it’s not hard to understand why the world doesn’t seem to be concerned with ancient lakes. But Jeffrey McKinnon would like to argue differently.

McKinnon explains that despite covering such a limited space, these lakes act as evolutionary museums, climate recorders, and biodiversity hotspots. For example, Lake Victoria, though much younger than Baikal or Tanganyika, has shown how quickly species can evolve. Over just 15,000 years, it has produced more than 500 species of cichlids — one of the fastest known cases of vertebrate evolution.

Meanwhile, Lake Baikal in Siberia contains more than 1,700 plant and animal species, two-thirds of which are found nowhere else. These include the Baikal seal (Pusa sibirica), the only exclusively freshwater seal species in the world, which probably adapted to lake life after being cut off from the ocean millions of years ago.

Within these lakes, there’s a microcosm of evolution. Scientists can track how species adapt to changes, compete for resources, and develop new survival strategies. In his book, called Our Ancient Lakes, McKinnon dives into fascinating discussions about how ancient lakes helped us better understand evolution, mutations, and even things like handedness.

But they’re also under threat.

Lakes are extremely vulnerable

Despite their resilience, many ancient lakes face serious threats from climate change, pollution, and invasive species. Rising temperatures reduce oxygen levels, affecting deep-water species. Fish species also have nowhere to go: the lake is their home, and it is inescapable.

A recent detailed extinction found that around a quarter of all freshwater species are threatened with extinction, and it’s not hard to see why.

Lakes can suffer terribly from industrial waste, tourism, and unsustainable fishing practices, endangering endemic species. Introduced species can disrupt delicate food webs. The Nile perch, for example, devastated native cichlid populations in Lake Victoria. The zebra mussel, a small mussel originally found in Russia made its way to North America. It arrived in the ballast water of a transatlantic freighter and colonized parts of Lake St. Clair. In less than ten years, zebra mussels spread to all five Great Lakes, wreaking havoc on ecosystems.

Conservation efforts — such as protected areas, fishing regulations, and pollution control—are crucial to preserving these lakes and their biodiversity. McKinnon’s book, Our Ancient Lakes, dedicates its final chapter to conservation, underscoring the urgency of protecting these irreplaceable ecosystems before it’s too late.

McKinnon’s words remind us why biodiversity matters — not just scientifically, but emotionally and ethically.

A few excerpts from the book:

“Ancient lakes are perhaps best known among biologists and certainly among students for providing case studies of adaptive radiation. Biology texts common feature a figure showing how cichlid fish in different African Great Lakes have evolved similar forms and appearances as they have adapted to similar diets and ecologies in different lakes. Those of us who have looked at figures of this sort time and again throughout our careers can easily start to take such con ergence for granted. But if I stop to reflect just a moment, it really is a wonder. From ancestors as genetically different from each other as we are from apes, fish in lakes hundreds of kilometers apart have evolved strikingly similar heads, body shapes, and fins when confronted by similar ecological challenges.”

“Baikal, or the Sacred Sea as it is known in Russia, is the largest, deepest, and most ancient of freshwater lakes. At Baikal’s beginning, usually considered to have been around 25 million years ago, our planet was a quite different place — the fauna, climate, and even continents were not as they are today.

If, for example, you were somehow to find yourself by the North American seaside of that time, you might encounter Pelagornis sandersi, a seabird with a wingspan of over twenty feet, about the same as an Andean condor and a wandering albatross placed wing tip to wing tip and measured together.”

“Biologists, economists, ethicists, and others from a range of backgrounds have ruminated deeply about why declining biodiversity should concern us, and why we should be willing to invest resources in arresting that decline. For myself, like many people, the issue is an emotional and moral one. I find joy and connection in the animals and plants I encounter in lakes, forests, and just my garden, and I find time in nature restorative. It also seems to me deeply immoral that we would accept the decline of the only biodiversity we know of, not just on this moist little rock but also on any planet anywhere. This view is at least shared by most major religions, though not discussed terribly often, unfortunately.”