We can still see these five traces of an ancestral species in all human bodies today
Many of us return to work or school after spending time with relatives over the summer. Sometimes we can wonder how we relate to some of those people with whom we seem to have nothing in common (especially with a particularly annoying relative).
However, in evolutionary terms, we all share an ancestor if we go back far in time. This means that many features in our bodies extend back thousands or even millions of years into our great tree of life.
In biology, the term “HomologyRefers to a similarity of structure based on ancestry from a common ancestor. Think of the similarities between a human hand, a bat wing, and a whale’s fin. All of these have specialized functions, but the basic body outline of bones remains the same.
This differs from “similar” structures, such as wings in insects and birds. Although they perform a similar function, dragonfly wings and parrot wings arose independently, and do not share the same evolutionary origin.
Here are five examples of ancient traits that you might be surprised to know still exist in humans today.
What makes us human? This question has baffled scholars and scientists for centuries. Today it seems relatively easy to tell who is human and who isn’t, but by looking at the fossil record things quickly become less clear.
Does humanity begin with the origins of our species, A wise manAnd 300,000 years ago? Or should we stretch things back over three million years to ancestors like “Lucy”(Australopithecus afarensis) from East Africa? Or even back to our separation from other great apes?
Whatever line you draw in the sand to define the birth of humanity, one thing is certain. The habitual act of walking on two legs, known as “bipedalism,” was one of the greatest strides of our ancestors.
Almost every part of our structure has been affected by the switch from walking on all fours to standing upright. These adjustments include the alignment and size of the bones of the foot, hip bones, knees, legs, and spine.
Most importantly, we know from fossil skulls that the rapid increase in the size of our brains It occurred shortly after I started walking upright. This requires pelvic changes to allow our larger-brained babies to pass through the dilated birth canal.
Our widened pelvis (sometimes called an iliac flare) is a symmetrical feature In common with several lineages of early fossil humansas well as all those who live today.
Then those great minds of ours fueled an explosion in art, culture, and language, which are important concepts when thinking about what makes us human.
hole in your head
In addition to your eyeballs sitting in their orbits, you might be surprised to learn that you have other large holes (known as fenestrae) in your skull.
There is one fenestra on each side of the human skull, uniting us with our skull Common ancestors more than 300 million years ago.
Animals that have this single window in their skulls are known as Synapses. The word means “fused arch,” a reference to the bony arch below the opening in the skull behind each eye.
Today all mammals, including humans, are synapses (but reptiles and birds are not).
Other famous prehistoric synapsids include the often misidentified Dimetrodon. The ancient, sail-supported reptile is often mistaken for a dinosaur. However, with their sprawling limbs and single temporal windows, they belong instead to a lineage sometimes referred to as “mammal-like reptiles,” although we prefer the more accurate term synapsids.
10 little toes and 10 little toes
I’m typing this article on my computer using ten of my digits (fingers and thumbs; the digits also refer to the toes but don’t hit the keyboard).
This pattern of five fingers on a human hand or foot, known as a “five-toed limb,” is found in most amphibians, reptiles, birds, and mammals.
But fish don’t have fingers and toes, so when did these fingers first develop?
a A recent study Myself and my colleagues have described the first digits to be found preserved inside the fin of a fish. We used powerful imaging techniques to look inside a 380-million-year-old fossil called… Elpistostege From Quebec, Canada, to reveal the oldest fish fingers!
Somewhat surprisingly, the first fish that evolved fingers still had fin rays around it, so these bones wouldn’t be visible on the animal from the outside.
The earliest tetrapods (four-limbed animals with a backbone that eventually moved from water to land) “experimented” with number digits, sometimes found with six, seven or eight.
It is likely that these early tetrapods still lived in the water. It wasn’t until tetrapods became truly terrestrial that the five-digit tip arrived. This arrangement most likely arose as a practical solution for the weight you bear on the ground.
Does your mind wander when brushing your teeth? Well, have you ever thought about how old your pearly whites are evolutionarily?
In 2022, a team of paleontologists describes isolated fossil fish teeth From Silurian rocks in Guizhou Province, China. This remarkable discovery pushed the minimum age of teeth back another 14 million years from previous findings. This means that our teeth now date back to 439 million years ago.
Named after that new fish, it is an early jawed vertebrate Qianod double It is known only from isolated, specialized teeth known as “appendages”. A spiral tooth is an odd row of teeth that curls in on itself in a spiral pattern (most famously in the buzzsaw shark, Helicoprion).
However, the teeth in the Chinese jawed fishes have a number of features found in other modern jawed vertebrates, which highlight their importance in understanding the evolution of our cockroaches. chomp on it!
The spine grows
“Growing a spine” means becoming bolder and more confident. The first animals to do just that must have braved the perilous ancient seas 500 million years ago.
First, these worm-like animals evolved a “notochord”—a rod built of cartilage that runs along the back of the body. This enabled masses of segmented musculature to be attached and a long tail extending beyond the anus. All animals with a notochord are called chordatesThey include everything from sea squirts to sea gulls, which are home to more than 65,000 living species.
To get an idea of the first chordates, today we can look at animals like Lancelet (known as Amphioxus or Brankyostoma). Lancelets look like small, primitive fish without fins. They swim by undulating their bodies from side to side.
Next come those with well-organized heads (cranios), and those in which the notochord is replaced by a backbone in adults (vertebrates).
The spine is made up of individual segmented bones (vertebrae) that fit together in a specific interlocking pattern. We have a puzzling few fossils that represent the earliest known examples of vertebrates, such as Metasprigina Known from Canada, or Haikouichthys From China in rocks over 500 million years old.
So whether it’s your large brain and wide pelvis from walking upright, a skull with a single nostril and bony arch, your fingers, toes, teeth, or spinal cord, we humans share many ancient features in our bodies.
and then, In the words of poet and activist Maya AngelouIt may be worth remembering that we are more alike than we are not alike.