Episode 18 – Human Evolution

Episode 18 can be found – in two parts! – on PodBean, iTunes, or Stitcher!

This episode topic comes requested by Mac, but we couldn’t bear to squeeze it into just one episode! We discuss the fascinating, complicated, and deeply personal story of Human Evolution.

In the News (from Part 1):
Plesiosaurs’ Four-Flippered Swimming
Researchers built a plesiosaur robot to demonstrate how these marine reptiles’ four flippers could most efficiently navigate the water. [Report]
The Life of a Dodo
Cutting through dodo bones allowed researchers to identify the yearly habits of dodos, including their molting and breeding seasons! [Report]
Eating With Weird Whale Teeth
A statistical analysis of the bizarre teeth of ancient whales suggests they were built best for slicing through prey, not filter-feeding as has been proposed. [Report]
Mutations and the Path of Evolution
A study reconstructed the ancestral form of hormone receptor proteins, and discovered that a key mutation was one of several hundred options, each with their own unique consequences. [Report]

Hominin News! (from Part 2):
Neanderthal Tooth Gunk
An analysis of the DNA from Neanderthal tooth plaque reveals not only what they were eating, but hints at the ways they may have been using plants and interacting with our own species. [Report]
Surprise Footprints
Footprints from the Mediterranean may represent the earliest true bipedal hominins, but not only are they in Europe, they’re way older than expected! [Report]
Where Do the “Hobbits” Fit?
A new detailed analysis of the island dwarf Homo floresiensis suggests this species has much more ancient roots than we previously thought. [Report]
A Sugary Secret to Human History
Researchers have discovered that a certain sugar molecule leaves a signature in ancient bone, and might be able to add new details to the history of human evolution. [Report]

The Story of Us

Humans are animals. And mammals. And primates. And apes.

Many of the features we have are inherited along with other primates from the same ancestors, including our forward-facing eyes, three-color vision, grasping hands, big brains, small faces, complex social structures, and more.

Ape Evolution
Our place among Primates! From early ancestors (bottom), all modern apes have developed, including ourselves! Images from Wikimedia Commons.

More specifically, we fit right in among the Great Apes (orangutans, gorilas, and chimpanzees+bonobos). All of the species closer to Homo sapiens than to any other living species (all descended from a common ancestor we share with chimpanzees around 6-8 million years ago) are commonly referred to as hominins.

An Astounding Fossil Record

The fossil record is always limited, but there are few evolutionary sequences as well-represented as hominin evolution. Thousands of fossils representing well over a dozen species range from the very recent past back to 6 or 7 million years ago. The fossil data for human evolution is so extensive that paleontologists (and more specifically, paleoanthropologists) are able to ask detailed questions – and have detailed debates – that are simply not possible for other ancient life.

Across the spectrum of hominin evolution, the fossil record presents an incredible view of the transition from the more typical ape-like features of our ancestors to the human-like features we have today: gradual changes in the teeth, jaws, braincase, arms, legs, spine, and even behavior.

Early Hominins
Early members of our lineage. Top left: Ardipithecus ramidus, ~4.5 million years old (Ma); Right: Australopithecus afarensis, ~3Ma (this is Lucy!); Bottom left: Australopithecus sediba, ~2Ma. Images: “Ardi” by Tiia Monto; sediba by Brett Eloff, Wikimedia Commons

Across the first few million years of hominin evolution, we witness a series of very ape-like species gradually accruing features that look more and more like modern humans.

Later Hominins
Within the past 2 million years, we see a huge diversity of the genus Homo, including early species like Homo erectus (left); ancient members of our own species, Homo sapiens (middle); and our close cousins and contemporaries such as Homo neanderthalensis (right). Images by Thomas Roches (Wikimedia), James St. John (Flickr), and Luna04 (Wikimedia).

Once the genus Homo appears, it diversifies into a wide array of species. Over the past two million years or so, there have been many populations of various species (or subspecies) of human living at the same time, and often in the same place, across Africa, Europe, and Asia. It’s only in the last 40,000 years or so that Homo sapiens has been alone.

skeleton-414543_1280
Compared to other primates, our human skeleton (left-most) is extensively adapted for upright walking. Image by stux, Pixabay.

Bipedalism (walking on two feet) was present in Australopithecus, and possibly even earlier, and continued to develop as hominin evolution continued. The human skeleton is highly modified compared to other primates, which features of the skull, spinal column, hips, knees, and feet all adapted in concert to allow us to walk in the very peculiar upright stance we use.

LaetoliS1prints4TC
Footprints from the famous Laetoli fossil site in Tanzania show that Australopithecus was walking upright by 3.7 million years ago. Image: Masao et al. 2016
Tools
The creation and use of stone tools goes back at least 2.5 million years. From early, simple cut stone, like the 1.7Ma Oldawan choppers on the left, to a huge diversity of implements like the 65,000 year-old fire-treated tools on the right. Images by Didier Descouens and Daleyhi, Wikimeda Commons.

There’s a LOT that we’ve learned about human evolution, and a LOT left to go. Have some links!

You can find tons of information about human evolution evidence and ongoing research at Becoming Human, the Smithsonian’s Human Origins page, and the London Natural History Museum.

Those websites are great, but some discoveries are so new they haven’t been included much in those kinds of sites, like Homo naledi and the Denisovans.

In this episode, we also mentioned a couple other things to check out:
The Leakey Foundation’s Origin Stories podcast is fantastic.
And here’s that capuchins TED Talk we referred to.

For more from us, follow Common Descent on Twitter, Facebook, and Patreon!

 

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2 thoughts on “Episode 18 – Human Evolution

  1. Hayley July 24, 2018 / 7:30 pm

    Bit of a later comer – but absolutely loved this episode of your podcast!
    When you were talking about the evolution of kissing at the end there it made me think of this presentation I came across by Greg Downey – where he mentions cross-cultural practices of “kissing” or alternatives. You can find the presentation here: https://prezi.com/w1lemos5j6fa/anth-207-sexuality/
    He reports 21/190 societies engaged in kissing on the mouth – and that prior to the spread of missionaries in some regions kissing was unheard of and alternatives like sniffing and grooming were common instead. INTERESTING!

    Like

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