A notochord, dorsal nerve chord, post-anal tail and pharyngeal gill slits. The Cambrian fossil Pikaia has all the features of a primitive chordate, which is the evolutionary precursor to all vertebrates.
And we humans are vertebrates, so does that mean this ancient worm/eel-like creature is our ancestor? Let’s find out by asking: Did humans evolve from Pikaia?
Did humans evolve from Pikaia?
No, humans did not evolve directly from Pikaia gracilens. Pikaia is a distant “invertebrate” relative of ours. (Yes, that “sea worm” might not be your ancestor, but you are related!)
As an early member of the chordate lineage, Pikaia lived alongside some of its relatives who would become true vertebrates – the ones that would become true fish, then amniotes, amphibians, reptiles, mammals and eventually, you.
However, the evolutionary path from ancient chordates like Pikaia to humans is long and involves numerous branches and intermediates.
Pikaia represents one of the earliest steps in that complex evolutionary journey, showcasing the first origins of the chordate metazoans whose body plans would eventually lead to all of us vertebrates.
What animal did humans evolve from?
We can’t actually say with 100% accuracy which individual animal species or families we evolved from because the time scales involved mean most of the fossils we’ve found represent offshoots and splits from the family line – not to mention those early ancestors diverged into other lineages, too.
But as an evolutionary thought experiment, we can say that humans are chordates and vertebrates. That means we come from early chordates (who might have been PIkaia’s contemporaries) who evolved into true vertebrates, which would in time become fish.
The early fish included gnathostomes (jawed fish), who would eventually become sarcopterygians (lobe-finned fish), who would eventually crawl onto land and become the first tetrapods, who became reptiles, a lineage of which would become synapsids, who would become mammals, diverging into primates and eventually, us humans.
What we do know is that, more recently, the primates we humans evolved from were part of the hominid group.
The most well-known of these are the genus Homo, such as Homo habilis and Homo erectus, which directly preceded Homo sapiens (us).
The evolutionary journey of humans is rooted in a common ancestor with chimpanzees and bonobos, our closest living relatives, approximately 6 to 7 million years ago (Prüfer et al. 2012).
What is the closest living relative to the Pikaia?
The closest living relatives to Pikaia are not single species but rather the entire subphylum Cephalochordata, which includes lancelets or amphioxus.
These small, fish-like marine animals exhibit key characteristics of early chordates, such as a notochord, a dorsal nerve cord, and gill slits, similar to those found in Pikaia. And they are still alive today.
Also discover if Pikaia had bones and whether Pikaia is a fish.
What is the oldest ancestor of humans?
In our most recent evolution, our oldest known primate (mammal) ancestor is believed to be Sahelanthropus tchadensis from about 7 million years ago.
Sahelanthropus tchadensis presents a mixture of human-like features and more primitive traits found in other primates, indicating it could represent a common ancestor of both humans and the lineage leading to chimpanzees (Brunet et al., 2002).
Our absolute oldest ancestor is sadly unknown – Cambrian stem vertebrates like Haikouichthys and Myllokunmingia as well as Zhongjianichthys are offshoots from the vertebrate line with no living relatives, so they are not our direct ancestors.
In fact, we can trace our broad ancestry back quite far, through the Mesozoic (dinosaur times) and even the Permian – our biggest problem with tracing direct ancestry comes in with the land transition when early tetrapods crawled out of the sea.
Most of the tetrapod fossils we have from the water-land transition are only representatives of the way it might have happened – the actual fossils we have from that time are not our direct ancestors, unfortunately.
If we could find our true Carboniferous tetrapod ancestors, we might be able to trace our true ancestry back even further.
Why is Pikaia special?
Pikaia is special because it is one of the earliest and most primitive chordates known from the fossil record, having lived during a part of the Cambrian period – our Pikaia fossils are from around 505-508 million years ago.
Its discovery in the Burgess Shale provided the first evidence of a notochord in a creature from the Cmabrian, underscoring its significance in the evolution of the vertebrates.
The notochord is a key feature that distinguishes chordates from other metazoan animals of that time. And it’s important for our understanding of evolution because chordate notochords are the precursors to the vertebral column we vertebrates share.
Discover loads more amazing insights into what is so special about Pikaia.
How old is Pikaia?
The Pikaia gracilens fossils we have are approximately 505 million years old, originating in the Middle Cambrian period. This time frame places it squarely within the “Cambrian Explosion”, a period of rapid evolutionary diversification among marine organisms.
Also see: Is Pikaia a fish?
When did Pikaia go extinct?
We don’t know when exactly Pikaia went extinct because we only have a few fossils of it from that one slice of time 505 million years ago.
It might have lived millions of years before or after that, but our fossil record of it begins and ends at that time.
Discover more: When did Pikaia go extinct?
We do know that there were changes in the marine ecosystems back then, and loads of more advanced forms were evolving at that time, too (including our vertebrate ancestors), so these things might have contributed to Pikaia’s extinction.
Based on the evidence, we conclude that Pikaia must have gone extinct. (You would become an overnight celebrity, though, if you were to go out right now and find a living Pikaia. But then again it’s the same with T Rex).
Also see: Did Pikaia have bones? And what did PIkaia eat?
Fossil Locations: Where Are Cambrian Fossils Like Pikaia Found?
- Pikaia itself is only known from the Burgess Shale in British Columbia, Canada
- Yet other Cambrian sites include the Chengjiang fossil site in Yunnan Province, China
- The Wheeler Shale in the House Range of western Utah, USA
- The Sirius Passet site in North Greenland is another critical location for understanding Cambrian life.
Museum Fossils: Where can you Go to See Early Chordate and other Cambrian Fossils?
If you live nearby or can make the trip, there are a few great places to go and see some of the first animals and eumetazoans, including bilaterians, protostomes, deuterostomes and chordates, for yourself…
1. The Burgess Shale
Did you know you can actually go to the Burgess Shale fossil sites in the Canadian Rockies yourself? You can book a guided hike with The Burgess Shale Geoscience Foundation and visit the Walcott quarry, Mt. Stephen – the works.
Phone 1 (250) 343-6006, email info@burgess-shale.bc.ca or visit their website
2. Royal Ontario Museum
The Royal Ontario Museum in Toronto, Canada is famous for its connection to the world-famous Cambrian site, the Burgess Shale. They have both an amazing fossil collection if you visit in-person or even here online and a cool virtual sea odyssey you can experience online right now.
Phone: 416 586 8000 (Canada) | or visit their website
3. Smithsonian National Museum of Natural History
The Smithsonian has quite a large Cambrian fossil collection. And it’s completely free! So, if you’re ever in Washington DC, it’s one of the coolest places to go check out Cambrian fossils.
4. Chengjiang Fossil Site Natural History Museum
Being in China, it’s a bit hard to track down English info, but the Chinese government says there is a Chengjiang Fossil Site Natural History Museum, with over 60’000 fossil specimens at its location in Xincun Road, Chengjiang county, Yuxi City in Yunnan province.
5. The Natural History Museum, London, UK
With a rich collection of fossils and exhibitions that trace the history of life on Earth, the London Natural History Museum’s displays on Cambrian and Precambrian life provide context for the evolution of complex organisms.
Phone +44 (0)20 7942 5000 or visit their website.
6. Field Museum of Natural History, Chicago, USA
Boasting a broad collection of fossils and active in paleontological research, its Evolving Planet exhibition takes visitors through the history of life on Earth, including the Cambrian period.
Phone +1 312 922 9410 or visit their website.
Documentaries Featuring some of the First Chordates
They’re not always 100% accurate because we make new scientific discoveries all the time. But documentaries at least deliver the gist of the information in a fun and engaging way. Just click play, hit full screen and enjoy hours’ worth of awesome documentaries on first animals, right here…
1. Walking with Monsters
BBC, 2005
A bit older now and flashing past early animals a bit too quickly, this one in the “Walking With” series is still pretty cool for its Cambrian bits. It’s also available via Amazon.
2. Mankind Rising
2012
The 2012 TV movie production of Mankind Rising is a single animated journey from the earliest vertebrates ancestors right through to present-day humans – it’s pretty cool, maybe a bit dated, but still a lot of fun!
3. David Attenborough’s Rise of Animals: Triumph of the Vertebrates
BBC, 2013
Although more focused on the evolution of vertebrates, it’s still an awesome documentary to watch. It’s available to purchase from Amazon.
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