Evolution

Same blueprint, different animals — and a family tree bush you can hold

The fastest evolution argument is a picture: one bone plan, reused everywhere. Then spin the skulls yourself in 3D and watch brain size, brow ridges, and faces change across the Homo family.

Homologous forelimbs — one plan: 1 bone, 2 bones, wrist, fingers

Forelimb skeletons of a human arm, dog foreleg, bird wing and whale flipper in four labeled panels, color-coded so the same humerus (gold), radius (blue), ulna (red), wrist bones (green) and hand and finger bones (purple) can be matched across all four — **Human arm · dog foreleg · bird wing · whale flipper — same bones, same order.** Humerus → radius & ulna → wrist bones → fingers, wildly different jobs: grasping, running, flying, swimming. The whale's “flipper” contains a humerus, radius, ulna, carpals and five digits made of finger bones. A designer starting from scratch doesn't put finger bones inside a flipper; common descent predicts exactly this. Homology = inheritance, not engineering efficiency. Ask: “Why does a whale need five fingers it can never use as fingers?”

Whale evolution, a fossil series: Pakicetus (~50 million years ago, land mammal with a whale's inner-ear bone) → Ambulocetus (the “walking whale”) → Rodhocetus → Basilosaurus (fully aquatic, with tiny external hind legs, complete with toes; a side branch, but its relatives gave rise to modern whales) → modern whales, which still develop hind-limb buds as embryos and carry a vestigial pelvis. Very rarely, a dolphin is born with small hind fins — documented off Japan in 2006 — atavism in action.

More key facts: Humans have 23 chromosome pairs, other great apes 24 — because human chromosome 2 is two ape chromosomes fused end-to-end, with a vestigial centromere and telomeres in the middle, exactly where fusion predicts them. Endogenous retroviruses sit at the same DNA addresses in humans and chimps — shared infections, inherited. And Tiktaalik was found in 375-million-year-old rock on Ellesmere Island because scientists predicted a fish-with-a-neck should be there, then went and dug it up.

Sources: Whale evolution · Ohsumi & Kato 2008, dolphin with hind fins (Marine Mammal Science) ·IJdo et al. 1991, chromosome 2 fusion (PNAS) · Human chromosome 2 · Endogenous retroviruses · Daeschler et al. 2006, Tiktaalik (Nature)

The Berlin specimen of Archaeopteryx, a slab fossil showing wing and tail feather impressions alongside a toothed skull, clawed fingers and a long bony tail — *Archaeopteryx* (~150 million years ago), the Berlin specimen: feathers and wings — plus teeth and a long bony tail no modern bird has, and clawed fingers on the wing. A transitional form is not a “half-bird”; it's a mosaic, exactly what evolution predicts and special creation doesn't.

Sources: Archaeopteryx

Spin the skulls — interactive 3D

Drag to rotate, scroll to zoom. Switch species and compare: braincase size, brow ridge, face projection, chin. Models are 3D scans of fossil casts and reconstructions hosted on Sketchfab; the full Smithsonian collection is linked underneath.

Australopithecus afarensis — composite cranium (the “Lucy” species). Small braincase (~375–500 cc), projecting face, large teeth. Model: Digital Atlas of Ancient Life, via Sketchfab. Open on Sketchfab ↗

Smithsonian 3D Hominin Fossils — full collection ↗ Smithsonian Neanderthal cranium in 3D ↗ Museum of the Earth — hominin 3D models ↗

Side views of fossil hominin skulls in rows, from Australopithecus africanus and A. sediba through Homo habilis, H. rudolfensis, H. floresiensis, H. naledi and H. erectus to an archaic and a modern human, each labeled by specimen and species, with a 10 cm scale bar — **Not a ladder — a bush.** Fossil crania from *Australopithecus africanus* and *A. sediba* through *Homo habilis*, *H. rudolfensis*, *H. floresiensis*, *H. naledi* and *H. erectus* to archaic and modern humans (figure from Hawks et al. 2017, eLife). Multiple hominin species lived at the same time for most of the last ~4 million years. Humans are apes, and chimps are our cousins, not our ancestors — we share a common ancestor with them, so “why are there still apes?” misunderstands the tree the same way “if Americans came from Europeans, why are there still Europeans?” does.

The family, side by side

Species	Lived	Brain size	What to point at
Australopithecus afarensis (“Lucy”)	3.9–2.9 million years ago	~375–500 cc	Walked upright with an ape-sized brain — bipedalism came first, big brains later
Homo habilis	2.4–1.6 million years ago	~510–700 cc	Associated with early Oldowan stone tools — though older tools exist (Lomekwi, 3.3 million years ago; Oldowan, 2.6–3 million) and which species made which is unresolved
Homo erectus	1.9 million – ~110,000 years ago	~550–1,250 cc	Among the first to spread out of Africa (Dmanisi, Georgia, ~1.8 million years ago); may have used fire (evidence from ~1 million years ago, clearer after ~400,000); body proportions like ours
Homo heidelbergensis	~700,000–200,000 years ago	~1,100–1,400 cc	Possible ancestor, or close relative of the ancestors, of Neanderthals and modern humans (its species boundaries and place in the tree are debated)
Homo naledi	~335,000–236,000 years ago	~465–610 cc	Small brain, human-like hands/feet — found 2013 (announced 2015) in South Africa's Rising Star cave; whether the bodies were deliberately placed there is debated
Homo floresiensis (“the Hobbit”)	~100,000–60,000 years ago	~380–417 cc	~1.1 m tall island species on Flores, Indonesia (stone tools until ~50,000 years ago) — likely island dwarfism, though some researchers think its ancestors were already small-bodied
Homo neanderthalensis	~400,000–40,000 years ago	~1,200–1,750 cc	Brains as large or larger than ours; made sophisticated tools and ornaments, with some evidence of deliberate burial (debated); ~1–2% of the DNA of people with non-African ancestry is Neanderthal
Denisovans	~200,000–50,000 years ago (end date uncertain)	Known from DNA, proteins and a few fossils	First identified in 2010 from DNA in a finger bone; a jaw from Xiahe on the Tibetan Plateau (~160,000 years old) and, in 2025, the Harbin skull have since been linked to them (the Harbin link is debated); their DNA persists in Melanesian and Tibetan populations (altitude gene EPAS1)
Homo sapiens	~300,000–315,000 years ago – now	~1,300–1,400 cc avg	Earliest widely accepted fossils at Jebel Irhoud, Morocco (~300,000–315,000 years ago), about 100,000 years older than the previous oldest sapiens fossils; the main migration out of Africa came ~60,000–70,000 years ago

Brain volumes are commonly published ranges for each species and vary by specimen.

Sources (Smithsonian Human Origins, then papers): A. afarensis · H. habilis · H. erectus · H. heidelbergensis · H. naledi · H. floresiensis · H. neanderthalensis · H. sapiens · Krause et al. 2010, Denisovans (Nature) · Hublin et al. 2017, Jebel Irhoud (Nature) · Reich et al. 2010, Denisovan genome (Nature) · Sutikna et al. 2016, Liang Bua dating (Nature) · Plummer et al. 2023, early Oldowan (Science) · Shen et al. 2009, Zhoukoudian dating (Nature)

Image credits — homology diagram: Vladlen666 (Волков Владислав Петрович), CC BY-SA 4.0 (recolored, relabeled and rearranged here under the same license); Archaeopteryx (Berlin specimen): Emily Willoughby, CC BY-SA 4.0; hominin skull comparison: Hawks et al. 2017, eLife, CC BY 4.0; 3D skull models via Sketchfab (Digital Atlas of Ancient Life; RLA Archaeology, UNC; Neanderthal V2) and the Smithsonian 3D Digitization program. Some images are resized or cropped.