Why are there no species that have developed to bridge the gap between humans and apes?
In: Biology
The answer is that they did.
We have an entire evolutionary chart and everything. [https://en.wikipedia.org/wiki/Human_evolution](https://en.wikipedia.org/wiki/Human_evolution)
If you are asking why there are none left alive today… we and nature at large killed them off.
To us, they were a threat and survival of the fittest ensued. To other threats, their intellect did not yet outmatch the most clever of predators. That is why all that remains are fossils.
We are, for all our intelligence, still animals. Early homo sapiens would have likely isolated from then warred against Neanderthal and our other predecessors if any remained.
Our common ancestor was waaay back on the evolutionary tree. We evolved to use our intellect to solve problems. Brute force worked well enough for their branch to succeed to the present day. There would have been links back to our common ancestor, but we only ever get to see a snapshot of what has existed on planet earth. The VAST majority of organisms that have existed have either evolved into a species better suited to its environment, or died out with no evolutionary offspring. Life is a product of its environment, and a static environment, when we’re talking of millions of years simply doesn’t exist. Many “homo” species have existed, but we did better.
Imagine back in the Roman times, one of your ancestors was deployed in a war and had a kid in (modern day) Turkey, then moved back home and had a kid in Italy. Maybe the Turkish kid’s children moved to Egypt while the Italian’s grandkids moved north into Europe. Skip forward 2000 years and you have people in Africa that share DNA with people in England that look vastly different.
Asking why there are no species to bridge the gap is like a white European asking where the brown person is that sits in between them and their black African distant relative. The gap was bridged centuries ago. Like how the gap between yorkshire terriers and Rottweilers was bridged thousands of years ago from wolves.
With apes and humans, the gap was bridged MILLIONS of years ago.
Snowball effect of various developments in human culture. You’re also thinking about this from a very anthropocentric perspective and measuring progress in a particular way. The progress from single celled organism into complex life is an incredible increase in ability and we draw the lines between the stages. The difference between apes and humans represents 6 million years worth of evolution. If you were to talk more specifically about earlier versions of man, rather than apes it would be more recent but even so, it’s still hundreds of thousands of years. It’s not like these things came about overnight, and drawing this arbitrary line ape vs human (humans didn’t even evolve from apes mind you) and saying how different they are doesn’t actually make much sense. Compared to what? Compared to the dominance of other animals when they were the most dominant on the planet? There are plenty of times in the history of the earth that certain animals or plants have absolutely dominated the ecosystem with almost no equal. Dinosaurs for instance.
Another thing to think about is what is your ability compared to an ape. You can do certain things better than him, you’re more dexterous, you can probably solve problems better than him, but if you were left alone who would be better at surviving? He’s way stronger than you and similarly resourceful and has much better natural tools to survive, is a better climber and fighter. What does ability even mean? You can teach apes to do lots of stuff we can do. We are only better because of the cumulation of thousands of years of humans working together and creating new things and designing a society which produces everything we could possibly need to survive, and far far more. If we suddenly wiped out all human knowledge and infrastructure, all concepts of language and everything the human race had learned and stored in society’s collective brain, and just put a load of infant or even young humans into the world, they wouldn’t do very well at all.
Overall though there are a few super important things which happened to advance civilisation heavily which is what separates us most from other animals:
Fire (cooking, not dying super young from disease, able to preserve food longer)
Language(form complex ideas and communicate)
Tools
Agriculture to allow for communities and more time not spent hunting safer more reliable
Transport wheels boats etc
Currency trade
Maths
Astronomy/ calendar
Science
Overall, instead of existing purely to survive like most animals, humans became able to spend more time and energy improving and were able to collaborate in communities formed by agriculture etc. language allowed us to actually express complex ideas. I think the ability to formulate thoughts into words in a systematic way allows for more complex thought and problem solving (drawing a problem typically is far easier than having to solve in your head)
When two species inhabit the same ecological niche, and compete for the same resources, in the long term only one can survive. The weaker one either moves to another niche or dies out.
The same happened with all the Home genus that existed between us and that common ancestor. The ape-side of the tree moved into a niche the homo-side didn’t want and survived, but the homo variants competed for the same niche.
It is a fair assumption knowing how we operate nowadays, but still only an assumption, to say that that competition for resources involved annihilation by force. The time span we’re talking about here is long enough that non-violent takeovers (i.e. having more and stronger people leads to monopolization of resources) would also have done the trick.
In addition, many of the branches would have been able to cross-breed and would have disappeared that way. Breed in enough of what would turn out to be the branch leading to Homo Sapiens and the other branch vanishes. (BTW We found a couple of gene pools in modern humans that proof that even Homo Sapiens picked up some closely related branches in certain regions.)
You also have to take into account that you’re not comparing the apes to us *today*, you’re comparing the apes to the original homo sapiens. There’s a lot of apes that are smart, but we managed to hit that critical mass of intelligence that let us build generational knowledge. That gap can’t just be attributed to genetics, but our education and accumulation of knowledge and culture.
Like others are saying, there’s evolutionary reasons the gap exists. But also the gap is not as large as you’re thinking.
I’ve read that our language ability played a huge part in it. As our ability to communicate in more complex and abstract ways grew, we were able to pass down knowledge, information and techniques to our descendants. It’s true that apes can learn from each other through imitation, but not through verbal instruction. Teaching through verbal instructions means I can call instructions to you from afar or teach you how to do something even if I can’t do it myself anymore.
I am just a layman so please correct me if I am wrong here but ultimately a lot of what you are asking in this are largely open questions being currently researched now by scientists in the appropriate fields. Something clearly unique happened to our lineage that set them apart so drastically from our closest relatives. But what event or events exactly where they? Thats not well understood.
So ELI5? Its a great question: we aren’t entirely sure.
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