We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is the Difference Between Monophyletic and Polyphyletic?

Michael Anissimov
Updated Feb 20, 2024
Our promise to you
AllTheScience is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At AllTheScience, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

In biological taxonomy — also called scientific classification or biological classification — monophyly means a group exclusively includes a species and all its ancestors, while polyphyly means a group may contain a "grab bag" of different families. These are called monophyletic and polyphyletic groups respectively. An example of a polyphyletic group would be "worms" or "warm-blooded animals," while a monophyletic group would be "mammals" or "crustaceans."

The history of biological taxonomy has been one of trying to eliminate polyphyletic groups in favor of monophyletic ones. Since the 1970s, this has been made much easier by genetic methods — also called phylogenetic analysis or "molecular studies" — which study similar lengths of DNA to find how animals are related to one another. Many groups which look superficially similar may be found to be entirely unrelated in practice. For instance, Pygopodidae, a family of legless lizards, appear similar to snakes but are distinguished from them by eyelids that blink (which snakes lack), external ear holes, flat, unforked tongues, and vestigal limbs. To the amateur, telling the difference can be somewhat difficult, but to a professional biologist it can be clear.

One of the most standard examples of a polyphyletic group are warm-blooded animals, which include both birds and mammals. Both species have a common ancestor that lived during the Paleozoic, a very long time ago. Birds, although warm-blooded, evolved from cold-blooded ancestors, the dinosaurs, which are hardly monophyletic with mammals. Thus birds and mammals are from entirely different groups, but both fall in the general category of warm-blooded animals.

Specific biological taxonomy is the goal of taxonomists, but often at odds with common wisdom or lack of rigor. For instance, when asked "Are there sea insects?" some might answer, "Well, sure, lobsters are kind of like insects." Although to a casual observer, this answer might seem sufficient, it's enough to cause a career taxonomist to practically spit out her coffee.

Insects are members of class Insecta, while lobsters are a member of subphylum Crustacea, an entirely different group. Although both are arthropods, and are probably related, the groups are quite different, with one being primarily terrestrial and the other aquatic. Casually referring to them as a monophyletic group is the sort of habit that taxonomists are fighting against by being more specific about relationships between animals, which helps us understand them better.

AllTheScience is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Michael Anissimov
By Michael Anissimov

Michael is a longtime AllTheScience contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Discussion Comments

Michael Anissimov

Michael Anissimov

Michael is a longtime AllTheScience contributor who specializes in topics relating to paleontology, physics, biology...

Read more
AllTheScience, in your inbox

Our latest articles, guides, and more, delivered daily.

AllTheScience, in your inbox

Our latest articles, guides, and more, delivered daily.