UsefulCharts Gets the Mammal Family Tree Wrong — and the Biggest Problem Is What It Calls Certain
Matt Baker's evolutionary chart promises to explain how mammals, including humans, came to exist. But several basic claims are demonstrably false, and some of its most important evolutionary relationships are presented with more certainty than the scientific evidence allows.
A family tree is an unusually persuasive way to explain evolution. Its branches make complicated relationships visible. Its labels give every organism a place. Its connecting lines suggest that scientists have worked out precisely how one lineage became another.
That visual authority comes with a responsibility: the distinctions between established facts, reasonable hypotheses, and unresolved scientific questions must survive the process of simplification.
In Evolutionary Tree of Life — Episode 3: Mammals (including Humans), published on October 11, 2024, UsefulCharts creator Matt Baker traces mammalian evolution from ancient synapsids through monotremes, marsupials, placental mammals, and eventually humans.
Much of that framework is sound. Mammals and reptiles share ancient ancestors. Mammalian ear bones evolved from structures associated with ancestral jaws. Humans belong to the great-ape family. Neanderthals, Denisovans, and modern humans exchanged genetic material.
These are important findings, and Baker makes them accessible.
But accuracy cannot be judged by how many statements in a presentation are correct. The crucial question is whether readers can trust the claims they are least equipped to check.
Here, the answer is less reassuring.
1. The Missing Marsupials: An Entire Continent Disappears
Baker introduces marsupials with a sweeping geographical claim:
“marsupial which again only live in Australia”
They do not.
Marsupials inhabit Australia, New Guinea, and the Americas.
The Australian Museum identifies more than 330 marsupial species, with roughly two-thirds living in Australia and most of the remainder occurring in South America.
The Virginia opossum, Didelphis virginiana, is a particularly embarrassing counterexample. This marsupial lives across substantial parts of the United States and extends into Canada. It is not a newly discovered creature or an obscure scientific exception. The Smithsonian National Zoo maintains an entire species profile describing its distribution.
The mistake matters because geographical distribution is central to Baker's explanation of mammalian evolution.
He connects the emergence of different mammalian branches to the breakup of ancient continents. That makes the actual locations of marsupials essential evidence, not incidental trivia.
A reader who believes marsupials exist exclusively in Australia receives a fundamentally distorted picture of their evolutionary history.
And there is a second mistake.
Baker explains that marsupials give birth to relatively undeveloped young, which subsequently enter a pouch and continue growing.
That is true of kangaroos and many other marsupials.
It is not true of every marsupial.
The Australian Museum explains that some marsupials possess only rudimentary skin folds instead of fully developed pouches. Australia's national science agency, CSIRO, identifies the short-tailed opossum as a marsupial without a pouch.
This distinction teaches something important: marsupial reproduction is more diverse than the familiar kangaroo model suggests.
Baker's simplified description removes that diversity.
The same geographical problem appears when he introduces monotremes.
He describes platypuses and echidnas as animals that both live in Australia.
The platypus does. Echidnas also inhabit New Guinea.
A genomic study published in Nature identifies four living echidna species distributed between Australia and New Guinea, including three long-beaked echidna species associated with New Guinea.
These are not disagreements about obscure fossil classifications.
They are errors about where living animals exist.
2. Australia Did Not Break Away First
Baker uses continental drift to explain why Australian mammals evolved along unusual paths.
His account contains another significant problem:
“with Australia coming off first which is why the mammals there are so different”
Australia was not the first component of Pangaea to separate into an isolated continent.
The geological history was substantially more complicated.
The Australian Antarctic Program explains that Gondwana began breaking apart around 130 million years ago. India, South America, and Africa separated while Australia maintained its connection with Antarctica until approximately 55 million years ago.
The Australian Museum provides an even more revealing picture of the early Eocene, 56–33.9 million years ago: Australia, Antarctica, and South America remained connected through southern landmasses and ecological corridors.
That is not a minor correction to the order in which continents drifted apart.
It changes the explanation of how animals reached Australia.
Research on monotreme evolution has identified fossil representatives in South America. Marsupial evolutionary history also involves movement through southern continental connections, including Antarctica.
Australia's extraordinary mammalian diversity cannot be explained simply by imagining it breaking away first and preserving an isolated collection of ancient animals.
The real story involves migration, changing land connections, ecological competition, extinction, and eventual isolation.
Baker's version is easier to remember.
Unfortunately, the version that is easiest to remember is not necessarily the one most faithful to geological evidence.
3. The Monkey That Breaks His Definition of an Ape
Baker makes another categorical claim while distinguishing monkeys from apes.
Monkeys, he explains, generally have tails. Apes do not.
So far, reasonable.
Then he goes further:
“apes are bigger and are the only mammals to lack Tails”
The second half is false.
Consider the Barbary macaque, Macaca sylvanus.
This monkey inhabits Morocco, Algeria, and Gibraltar. It lacks a visible external tail, retaining only a short vestigial structure.
The Natural History Museum in London specifically warns that its absence of a visible tail has led people to mistakenly call it a Barbary ape.
It is not an ape. It is a monkey.
The distinction is fundamental.
Apes can be characterized by their absence of external tails, but the absence of a tail does not establish that an animal is an ape.
The evolutionary classification of an animal depends on ancestry and multiple anatomical characteristics, not a single visible feature.
This is exactly the kind of distinction an evolutionary tree is supposed to teach.
Instead, Baker transforms a useful generalization into a false universal rule.
The problem is not that the Barbary macaque invalidates the evolutionary distinction between monkeys and apes.
It is that the distinction remains valid for reasons more sophisticated than Baker's explanation.
A good educational presentation should clarify those reasons rather than replace them with a rule that fails when confronted with a living animal.
4. The Mammalian Skull: A Real Discovery, a Questionable Explanation
One of Baker's strongest sections concerns the evolution of mammalian skulls.
He correctly explains that bones associated with ancestral jaw structures eventually became part of the mammalian middle ear.
This is among the clearest anatomical examples of evolutionary transformation.
But his account becomes less reliable when he discusses the secondary palate.
The secondary palate separates the oral cavity from the nasal passages.
Baker describes this adaptation as allowing mammals to smell substantially better than reptiles and birds.
That is not the principal evolutionary function established by the anatomical evidence.
A 2023 scientific review by Luke Norton, Fernando Abdala, and Julien Benoit, published in Philosophical Transactions of the Royal Society B, discusses the secondary palate in relation to structural reinforcement of the snout, more effective chewing, and the ability to process food while continuing to breathe.
Those developments may have contributed to the evolution of higher metabolic demands in mammalian ancestors.
Smell is an important mammalian sense, but separating the nasal and oral cavities does not, by itself, establish that mammals evolved superior olfaction to birds and reptiles.
Baker connects an anatomical development to an appealing functional explanation without distinguishing the demonstrated mechanism from the broader interpretation.
That distinction becomes even more important when discussing behavior that cannot be directly observed in extinct animals.
The video proposes that small, nocturnal mammalian ancestors survived dinosaur dominance partly because they could hide more effectively.
This is a reasonable evolutionary hypothesis.
It is not a complete explanation of early mammalian survival, nor does it establish that every associated anatomical change was driven primarily by nocturnal life.
Fossils preserve bones and other physical evidence. Reconstructing the precise behavior, sensory experience, and selective pressures of long-extinct animals requires further inference.
A presenter can explain those inferences without pretending they are observations.
In evolutionary biology, the difference is essential.
5. A Fascinating Theory About Milk Becomes a Historical Fact
Baker offers one of the episode's most memorable explanations when discussing mammary glands.
He states that mammalian mothers originally used milk-like secretions to keep their eggs moist rather than nourish their young.
There is substantial science behind that idea.
Olav Oftedal, a researcher associated with the Smithsonian, developed an influential hypothesis that mammary secretions evolved from ancestral skin glands that helped prevent soft-shelled eggs from drying out.
His 2012 review in Animal discusses how these secretions may subsequently have acquired antimicrobial and nutritional functions, eventually developing into the complex milk produced by modern mammals.
This is an excellent subject for a popular science video.
The problem is its presentation as a settled sequence of events.
No scientist observed the first mammary secretions hundreds of millions of years ago. The evolutionary reconstruction draws on comparative anatomy, developmental biology, molecular evidence, and the reproductive characteristics of surviving mammals.
The egg-moistening explanation is scientifically grounded, but its precise historical sequence remains inferential.
Baker could have preserved the entire educational value with one qualification: researchers have proposed that mammary secretions initially helped prevent eggs from drying out.
Instead, the narrative becomes something that definitively happened.
That is a recurring weakness in the episode.
An interesting hypothesis gains the authority of an established fact simply because the narration removes the uncertainty.
6. The Placental Family Tree Is Less Certain Than the Chart Suggests
The most consequential problem is not a missing marsupial or a tailless monkey.
It concerns the structure of the evolutionary tree itself.
Baker divides placental mammals into two large groups: Boreoeutheria and Atlantogenata.
He connects their evolutionary origins to Laurasia and Gondwana, respectively, using continental separation to explain the deepest divisions in placental mammal ancestry.
This is a legitimate scientific model.
But it is not the only model supported by research.
A major study published in PLOS Biology in December 2019 examined evolutionary relationships across approximately 6,000 living mammal species.
Its researchers did not recover a single completely unambiguous arrangement for the deepest placental branches.
Under one analysis, the Atlantogenata arrangement received a posterior probability of 0.53, compared with 0.47 for an alternative in which Afrotheria branches off first.
Those numbers describe support within that particular statistical model. They are not universal probabilities that one evolutionary history is correct.
They nevertheless establish something unmistakable: the placement of the earliest placental branches remained uncertain.
That uncertainty existed years before Baker's October 2024 presentation.
The distinction between a phylogenetic relationship and a historical geographical explanation also matters.
Even if two groups evolved predominantly on different ancient landmasses, their modern distribution does not independently prove that continental separation caused the original evolutionary split.
Researchers have considered competing explanations involving migration, rapid diversification, and evolutionary relationships that are difficult to resolve because ancestral populations separated over relatively short intervals.
Some studies favor the Atlantogenata arrangement. Others have recovered different relationships or substantial uncertainty.
The appropriate conclusion is not that Baker chose an indefensible tree.
It is that he presented a defensible evolutionary hypothesis as though the deepest branches had already been conclusively settled.
For an educational product built around a family tree, that matters more than a minor mistake in terminology.
A family tree is only as trustworthy as the certainty assigned to its branches.
7. Human Evolution Is Not the Straight Line Baker Draws
Near the end of the episode, Baker moves into the evolution of humans.
Here, the presentation becomes especially vulnerable.
He describes an evolutionary progression from australopithecines through Homo habilis, Homo erectus, and an African lineage leading through Homo heidelbergensis toward modern humans.
He also presents Homo heidelbergensis as the common ancestor of Homo sapiens, Neanderthals, and Denisovans.
That classification reflects a genuine and influential interpretation of the fossil record.
But it is disputed.
The Smithsonian Institution's Human Origins Program identifies Homo heidelbergensis as a likely candidate for the ancestry of modern humans and Neanderthals.
Crucially, its own educational material also asks whether fossils assigned to that species actually represent more than one evolutionary group.
Baker's explanation largely removes this uncertainty at precisely the moment readers most need to understand it.
And subsequent research has made the problem harder to ignore.
A 773,000-Year-Old Challenge From Morocco
On January 7, 2026, researchers led by Jean-Jacques Hublin published new findings in Nature concerning ancient human fossils discovered near Casablanca, Morocco.
The fossils date to approximately 773,000 years ago.
Their anatomy combines ancestral characteristics with features resembling later African and Eurasian human lineages.
The researchers argue that these remains provide important evidence concerning African populations close to the ancestry of Homo sapiens.
More importantly for Baker's evolutionary diagram, they explicitly challenge the assumption that fossils traditionally grouped under Homo heidelbergensis necessarily represent one coherent species.
The paper explains that some Eurasian fossils historically assigned to Homo heidelbergensis may belong more closely to Neanderthal and Denisovan ancestry without necessarily representing the lineage ancestral to modern humans.
This does not establish a definitive replacement family tree.
It demonstrates why such certainty was premature.
Genetic evidence indicates that the ancestors of modern humans, Neanderthals, and Denisovans diverged hundreds of thousands of years ago. The precise ancestral populations, their geographical distribution, and their formal species classifications remain subjects of investigation.
Baker cannot reasonably be criticized for failing to mention a study published in 2026.
He can, however, be criticized for presenting an already disputed ancestry as an established historical sequence in 2024.
The newer research exposes the weakness of that approach.
Denisovans: What a Single Skull Changed
The Denisovan section provides another revealing example of how quickly evolutionary knowledge can develop.
Baker describes Denisovans as an ancient human group known from a very small collection of fossils.
That was a reasonable characterization when his video appeared.
But in June 2025, researchers published two important studies concerning a nearly complete ancient human skull discovered in Harbin, China.
One study, published in Science, recovered 95 ancient proteins from the skull. Some protein variants closely connected the individual to Denisovans.
Another study, published in Cell, recovered Denisovan mitochondrial DNA from calcified material preserved on the skull's teeth.
Together, the findings provided strong molecular evidence connecting the Harbin individual, previously classified as Homo longi, with the Denisovan lineage.
For decades, researchers had struggled to reconstruct Denisovan anatomy because available remains were so fragmentary.
The Harbin evidence supplied something extraordinary: a nearly complete skull associated with the lineage.
The discovery did not settle every question about Denisovan classification or ancestry.
It made those questions considerably more interesting.
And it demonstrated something a static evolutionary chart struggles to communicate.
Human evolutionary history is reconstructed from incomplete evidence that can change dramatically when a single fossil receives a new analysis.
The appropriate response is not to abandon evolutionary trees.
It is to stop presenting their disputed branches as permanent conclusions.
8. The Real Failure Is Not Simplification. It Is False Certainty.
There is an obvious defense of Baker's presentation.
It is an introductory educational video, not a scientific journal article.
Nobody reasonably expects a 20-minute overview of mammalian evolution to address every disputed fossil, genetic analysis, or competing phylogenetic model.
That defense has merit.
A general audience needs clear explanations. A presentation overloaded with qualifications can become difficult to follow.
But this defense cannot excuse saying marsupials exist only in Australia.
It cannot make Australia the first continent to break away from Pangaea.
It cannot turn a tailless monkey into an ape.
And it cannot transform contested evolutionary relationships into facts merely because acknowledging uncertainty would complicate a diagram.
These failures do not all carry equal weight.
The geographical and anatomical mistakes are straightforward factual errors. They should have been corrected before publication.
The explanations of lactation and the secondary palate suffer from a different problem: they give viewers insufficient information about what the evidence actually establishes.
The deepest evolutionary relationships present the most serious editorial issue.
There, the very structure of the family tree gives disputed interpretations the appearance of certainty.
UsefulCharts sells printed versions of its evolutionary chart, an ordinary commercial activity that does not establish any improper influence over the content.
But publication as a durable reference makes scientific accuracy more consequential.
A viewer may forget a sentence.
A diagram can remain on a classroom wall for years.
The Verdict: An Attractive Map Is Not the Same as Accurate Science
Matt Baker is right about the foundations of mammalian evolution.
Mammals share ancient ancestry with other vertebrates. Synapsids preceded modern mammals. Evolution transformed jaw structures, reproductive systems, and countless anatomical features. Humans are one surviving branch of a much larger evolutionary history.
Nothing uncovered here undermines those conclusions or the scientific evidence for evolution.
The criticism is more precise.
Baker's presentation contains demonstrably incorrect statements about living mammals, an inaccurate account of Australia's geological separation, questionable explanations of anatomical adaptations, and insufficient qualifications around disputed evolutionary relationships.
These problems were not all created by research published after the video appeared. Several were identifiable using established scientific sources available before October 2024.
The most revealing mistake is the treatment of human ancestry.
The actual scientific story is one of competing hypotheses, incomplete fossils, genetic exchange between ancient populations, and discoveries that continue to change how researchers understand the past.
That story is not weaker because scientists admit uncertainty.
It is stronger because they investigate it.
An evolutionary tree should help readers distinguish what scientists know from what they are still trying to discover.
UsefulCharts succeeds at showing the branches. It is considerably less reliable at showing which branches remain uncertain.
And when an educational chart makes uncertainty invisible, it risks teaching something science itself is designed to resist: confidence without sufficient evidence.
References
1. Original work — Evolutionary Tree of Life | Episode 3 — Mammals (including Humans). UsefulCharts, Matt Baker, October 11, 2024. Watch the original episode
Primary material examined. Establishes Baker's explanations of marsupial distribution, continental separation, primate classification, mammalian anatomy, and human evolutionary ancestry.
2. What Is a Marsupial? Australian Museum, updated November 2, 2018. Read the Australian Museum's explanation
Documents the geographical distribution of marsupials and establishes that not all species possess fully developed pouches.
3. Virginia Opossum. Smithsonian's National Zoo and Conservation Biology Institute, undated species profile. Read the Smithsonian species profile
Confirms that living marsupials inhabit North America, including the United States and Canada.
4. Platypus and Echidna Genomes Reveal Mammalian Biology and Evolution. Nature, 2021. Read the genomic study
Establishes that living echidnas inhabit New Guinea as well as Australia and examines the evolutionary distinctions between monotremes and other mammals.
5. Antarctic Prehistory. Australian Antarctic Program, Australian Government, undated. Read the geological history
Documents Gondwana's breakup and Australia's prolonged geographical connection with Antarctica, contradicting the account that Australia separated first.
6. The Eocene Epoch (56–33.9 Million Years Ago). Australian Museum, updated January 23, 2020. Read the Australian Museum's geological reconstruction
Describes the southern continental connections that permitted movement between Australia, Antarctica, and South America.
7. Barbary Macaques: Europe and North Africa's Last Monkeys. Natural History Museum, London, undated. Read the Natural History Museum's account
Identifies a living monkey without a visible tail, disproving the claim that taillessness is exclusive to apes.
8. Craniodental Anatomy in Permian–Jurassic Cynodontia and Mammaliaformes. Luke Norton, Fernando Abdala, and Julien Benoit. Philosophical Transactions of the Royal Society B, 2023. Read the scientific review
Examines the anatomical evidence connecting jaw structures, the secondary palate, chewing, respiration, and mammalian evolution.
9. The Evolution of Milk Secretion and Its Ancient Origins. Olav Oftedal. Animal, March 2012. Read the research review
Explains the scientific hypothesis that mammary secretions originally helped protect eggs from dehydration before evolving more substantial nutritional functions.
10. Inferring the Mammal Tree: Species-Level Sets of Phylogenies for Questions in Ecology, Evolution, and Conservation. Nathan Upham, Jacob Esselstyn, and Walter Jetz. PLOS Biology, December 4, 2019. Read the phylogenetic study
Provides quantitative evidence of unresolved relationships near the root of the placental mammal evolutionary tree.
11. Homo heidelbergensis. Smithsonian Institution, Human Origins Program, undated. Read the Smithsonian's human ancestry profile
Identifies Homo heidelbergensis as a possible ancestor while acknowledging uncertainty over its classification and the relationships among associated fossils.
12. Early Hominins From Morocco Basal to the Homo sapiens Lineage. Jean-Jacques Hublin and colleagues. Nature, January 7, 2026. Read the original research
Describes approximately 773,000-year-old Moroccan fossils and challenges overly simple interpretations of the ancestry shared by modern humans, Neanderthals, and Denisovans.
13. The Proteome of the Late Middle Pleistocene Harbin Individual. Qiaomei Fu and colleagues. Science, June 18, 2025. Read the protein analysis
Reports ancient proteins recovered from the Harbin skull that connect its individual to the Denisovan lineage.
14. Denisovan Mitochondrial DNA From Dental Calculus of the >146,000-Year-Old Harbin Cranium. Qiaomei Fu and colleagues. Cell, July 24, 2025. Read the genetic study
Provides independent molecular evidence linking a nearly complete ancient human skull to Denisovans and expanding knowledge of their physical appearance and geographical distribution.