In 1857, the German anatomist Hermann Schaaffhausen analyzed a human fossil with "an extraordinary form" that he had never seen before – not in "existing European stocks", he wrote, or "even in the most barbarous races."
The curious cranium had been unearthed the year before, just east of Düsseldorf, in Germany's Neander Valley.
The remains were to become known as the world's first Neanderthal, and from the very start, Schaaffhausen decided the skull was at a "low stage of development".
For more than a century, that stigma has stuck around. Even today, a commonly accepted hypothesis is that humans outsurvived Neanderthals because of our better brains.
An international team of anthropologists has now found evidence to the contrary.
They have compared brain scans from two populations in the US and China to show that regional volume differences in modern humans are greater than those between Neanderthals and us.
The volume differences that separate Neanderthal and modern human brains are extremely small.
"If the Neanderthal differences are held to be cognitively and evolutionarily relevant, then similar neuroanatomical differences commonly found between modern human populations would also need to be considered cognitively and evolutionarily relevant," the authors point out.
But cognitive ability is only very weakly associated with brain anatomy in modern humans, if at all, the researchers explain, after reviewing the existing literature.
"If we reject the idea that these modern human populations are cognitively different in an evolutionarily meaningful way, then it would undermine any argument that Neanderthal differences should be considered so," they conclude.
When Schaaffhausen first published his opinion on the Neanderthal cranium in the mid-1800s, there was little evidence to suggest that humanity was any older than about 6,000 years.
What's more, it would be two more years before Charles Darwin published his seminal book, On the Origin of Species, in which he shared his theory of evolution with the larger scientific community.
The initial assumptions made by Schaaffhausen and his colleagues are clearly outdated.
In recent years, scientists have found evidence that while modern humans thrived and Neanderthals went extinct, that was not necessarily due to our brains.
Archaeological evidence is stacking up to show that Neanderthals were smarter than we once assumed, even though the shape and size of their brains differed from our own.
There are compelling signs that these ancient humans were swimming for shells on the ocean bottom, using tools to make fire, brewing antibacterial medicines, glue, or water-repellent substances, tailoring their own clothes, and even creating abstract art.
Oftentimes, Neanderthals were partaking in these practices well before modern humans.
Some evidence from their skulls even suggests that Neanderthals were capable of human-like speech, although that is very hard to garner from a few very old bones that once surrounded the ear.
"Speculation on Neanderthal cognition based on archaeological and paleoneurological research has frequently concluded they were likely cognitively challenged," write the authors of the recent brain analysis.
"Putting estimated Neanderthal differences into the context of modern human variation does not support this view."
Plus, it's worth remembering that Neanderthal skulls can only tell us so much about the intricate organ that they once housed. Even bones can be misinterpreted.
In recent years, some scientists have disputed the whole idea that Neanderthals were stooped, brutish cavemen who resembled apes more than humans.
Their posture was actually quite upright, according to recent analyses of their rib cages and hips, and at least in some cases, they seemed to have similarly sized chests.
Today, some scientists hypothesize that Neanderthals never actually went extinct, at least not in the genetic sense. Instead, they may have been close enough to modern humans to be considered the same species.
We certainly seem to have reproduced with each other for thousands of years. It's possible that our 'cousins' simply became subsumed within our own lineage. Hence why so many of us today still carry Neanderthal genes.
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If we continue to assume that Neanderthals were dim-witted and slow, incapable of speech or abstract thought, we only underestimate our own ancestry.
In many ways, we are one and the same.
The study was published in PNAS.