Obligatory HHGTTG reference
The answer is white mice, with dolphins an honorable second.
You seem to have staked out a position and now are simply hand waving away any evidence that challenges that position. At least two of the animals listed in the OP are regular tool users. I’ll leave it as an exercise for the student to re-read the OP and figure out which ones those are. 
Well yeah…that’s pretty much my usual modus operandi. 
And then, when I’m proven wrong (again) I can gracefully concede that I don’t have a clue what I’m talking about and go on to my next evil plan. I should be played by the cartoon character from Megamind instead of a combination of Lou Diamond Phillips and Jackie Chan as I asserted in another thread.
Seriously, it’s a debate. Feel free to argue…that’s what I’m here for after all. What indications do YOU think there are for any of the animals in the OP filling a human niche? What aspects of humanities niche do you see them filling? It’s not enough to say that any species COULD evolve to eventually become technology oriented tool users, since that’s obviously always a possibility. However, in the history of the world and based on current archeology, no other line of species has ever used tools the way hominids have. We’re pretty much unique. There have been other species that have filled the exact same niche as, say, wolves and lions, elephants
Elephants, rats and ants? Well, that’s 3. I think dolphins also use tools sometimes, though perhaps not in the wild. Octopi also, IIRC, but that would be 4. But they aren’t tool MAKERS…they just pick up whats laying about and use it then discard it. There is, afaik, no concept of teaching others of their species to use a tool in a certain way that would lead to actually making the thing.
Any of them COULD eventually fill a human niche (well, species that might evolve from them obviously), but I don’t see anything compelling to indicate that they would.
-XT
I seriously doubt this considering the fact that the Sahara gets virtually no rainfall. What cite do you have that humans so impact the climate as to turn huge swaths of forest into barren desert?
Acheulean tool use/manufacture has been (tentatively) documented as far back as 1.8m years (with 1.65m years being generally accepted), but it’s predecessor, Oldowan, has been documented as far back as 2.6m years.
Chimps with machetes. They learn fast when there is a need.
Who mentioned forest?
Oh Jesus Christ. Fine, replace forest with “savannah woodland” in my post.
In that case it makes no sense at all. The Sahara did get enough rainfall to be virtually all savanna woodland 10, 000 years ago.
It’s your claim:
You’re the one saying that no humans means that the Sahara would remain savanna woodland.
That’s right. And after three posts I still can’t figure out what *your *claim is.
Surely it can’t be literally what you said: that the Sahara always received virtually no rainfall and could never have supported savanna woodland. That is something that is incontrovertibly wrong.
Would it be too much to ask for you to stop being coy and just tell us what your point is?
What is coy about this?
You’re claiming that, if not for humans, the Sahara would be forest today. What is your cite for this?
For the second time, nobody ever mentioned forest.
Since your appear to have no intention of telling m what your actual point is, and since it appears you only want to put words in my mouth, I believe I shall leave you to it. Other can read for themselves what I actually posted.
Have fun.
Blake, on the basis of a very quick look it seems as though the Sahara is currently desert because rainfall decreased a few millennia ago, causing the savannah to die out. Is it your contention that this happened the other way around - that burning out the savannah led to desertification and decreased rainfall?
Basically, yeah. It’s the same process that’s been well established for Australia and Madagascar. These regions are all what are known as anticyclonic zones: weak monsoonal climates, in simple terms they are potentially subject to monsoonal weather patterns, but that can be broken up very easily by fairly minor fluctuations in temperature and humidity. One of the key attributes of these regions is that rain begets rain, and drought begets drought. Wet years tend to be followed by increasingly wet years and dry years by increasingly dry years until the weather system undergoes a spectacular collapse and resets itself to another phase.
Woody vegetation tends to moderate this pattern a lot. The vegetation coats the ground with litter that prevents rapid evaporation, the deep roots of the trees and shrubs allow the air to remains humid even at the end of the dry season and the live leaf cover increases albedo leading to rapid rises in temperature in spring. All those things together allow the monsoonal influence to extend much more freely. The first coastal monsoon showers wet the ground, and the warm humid air allows subsequent monsoon systems to penetrate deeper and deeper inland. Remove the woody vegetation and the monsoon systems breaks down over the coast and can’t penetrate inland.
In the case of the Sahara it the effect of burning was probably mostly felt within the gallery forests and coastal monsoon forests. The loss of the savanna itself seems to have been caused by the associated drying exacerbated by people moving domestic browsing animals into the savannas as the climate dried, a process that is still occurring throughout the Sahel.
As with all weather patterns, there are other factors in play. But we know that the current situation in the Sahara is highly anomalous, and given that humans have had the same influence in similar anticylconic zones elsewhere, it seems certain that humans are responsible. For example, the Sahara has never in the last few million years been further North than it is now, and has only very, very rarely been drier. In the past it only ever got this dry and this far north during glaciation events. Yet paradoxically it began moving north and drying out at the *end *of the last glaciation event, yet coincident with human vegetation change. Beyond all reason the Sahara is larger now than it was 15, 000 years ago at the height of the last glaciation when we would expect it to be *at worst *mildly drier than it was 8, 000 years ago and would probably expect it to be wetter. The last drying event in the Shara also occurred extremely rapidly, in some regions it appears to have tipped from humid to arid in less than 2, 000 years. This is much faster than the drying trends seen elsewhere on Earth at the time or any past events in the Sahara.
Prove that.
Maybe not octopii, but maybe walrii. Just sayn’. 
If octopuses didn’t become sentient by now, it isn’t because of us standing in their way. Unlike most other animals mentioned in this thread, there’s hardly any interaction between our two species, and we only started making an impact on them in the last 100 years.
Horses are right out. Their intelligence is far too low for them to evolve into anything remotely sentient, and their having hooves precludes them from ever evolving useful manipulators.
Except that humans didn’t really occupy any niche, we created one.
Humans in the “natural state” are just generalist omnivores. Our niche isn’t significantly different from that of foxes or pigs or bandicoots. So without humans there still isn’t any environmental niche for any other species to exploit.
I think this is a point that a lot of people are overlooking. Arguing about what species would occupy the human niche in the absence of humans is like arguing about what species would live in all those empty termite mounds if termites vanished. It doesn’t really make any sense because humans created the human niche, just as termites created the termite niche.
It’s not like hypothesising what animals might be eating all the grass if there were no ungulates on earth. Humans aren’t exploiting some food source or habitat type that wasn’t already being successfully exploited by dozens of other medium sized mammal species.
We might speculate on how those mammals have differed in the absence of human competiti0on, but suggesting that there is some sort of human-shaped hole in the African savanna ecosystem available for filling simply isn’t true.
Further to what **Blake **just posted… There isn’t anything preventing other animals from getting smarter even with us on the planet, much less all the other primates. Sure, we’re an apex predator and we destroy a lot of environments, but it’s not like our intelligence precludes other intelligences from evolving as if there some biological equivalent of the Pauli Exclusion Principle.