Tribes is a term that is not accepted by Africanists, as the term has a problematic history and gets applied so loosely that it carries no real meaning
Africans were not 'stuck in the stone age'. The Nok culture of Nigeria demonstrated iron-working by 500 BC, perhaps earlier. Iron working had spread all the way to the Limpopo river in South Africa by 1000 AD.
Many African states including Mali, Songhai, Ethiopia, Swahili, Nubia, Great Zimbabwe, etc. were engaged in trade or intellectual exchange with the wider world for centuries before Portuguese exploration began in the 1400s.
Here are two pertinent answers:
And you can find more in the FAQ. The general gist of these answers is that there's no reason to expect that they should have followed the same developmental path as Europeans or Asians, and despite that some of these societies did make many of the same advancements, as well as making completely different advancements that didn't happen in Europe or Asia.
There have been a few posts (since removed) that have recommend Jared Diamond's Guns, Germs, and Steel or a recent CGP Grey video based on that book. Most of these posts were removed for breaking our rules ("Avoid only recommending a source – whether that's another site, a book, or large slabs of copy-pasted text"), but in general we at /r/AskHistorians do not regard Guns, Germs, and Steel as a reliable source of history (see the relevant section of our FAQs).
That said, at least an aspect of what Diamond is writing about is at play here - namely diffusion, the process by which ideas and materials spread from culture to culture to culture. For example, the gunpowder spreading from China where it was originally invented (by alchemists attempting to invent something else entirely) all the way to Spain by the time Columbus sets sail. Another example would be corn spreading out from southern Mexico, heading south into the Andes and the Amazon and north toward the Great Lakes. According to Diamond, of all continents, Eurasia was best suited for allowing ideas to spread far and fast.
There may be a kernel of truth here, but the situation is far more complex than that. Diamond severely underestimates how quickly ideas can spread in the Americas, for example (wheat spreads across Europe from the Middle East around the same time that maize spreads from Mexico to Peru).
There's also the issue of whether, once exposed to a foreign concept, a culture actually adopts it. Australia wasn't nearly as isolated from the rest of the world as people like to think. Around 4,000 years ago there was wave of migrants from India that left their mark in Australia's genetic tapestry; traders from Southeast Asia were sailing off the northern coast of Australia for at least hundreds of years prior to European colonization; and for thousands of years, Torres Strait Islander peoples have been mediating trade between Papua and Australia. Despite that, there are no bows in Australia. Bows had been invented in Africa after the ancestors of the Australians and the Americans had left. Americans likely developed some version(s) of the bow independently but these models didn't really catch on until bows that ultimately descended from the original African concept, crossed into the Americas with the Inuit and Yupik. In Australia, the bow reached Papua and the Torres Strait, but seems to have stopped there. The people of Cape York certain knew of the bows used by their neighbors to the north, but they didn't adopt them for themselves. Between the woomera [spear thrower] and the boomerang (both of which come in a variety of forms across Australia) likely filled the "projectile weapon" niche in such a way to make bows redundant.
On a similar note, prior to the arrival of the Spanish, the Aztecs knew of bronze and how to make it - they just couldn't do it because the neighboring Tarascan State to their west had a monopoly on the resources needed to do so and weren't in the mood to share with their enemies. Regardless, even if the Aztecs could secure access to the tin and arsenic they needed to turn copper in into bronze, they might not have used it to make weapons. Metals throughout the Americas were generally funneled into other projects (ceremonial and ornamental for the most part) rather than utilitarian purposes because the cultures valued these materials differently than their Eurasian counterparts.
Again, the FAQs have a lot of threads on this and related topics and there's the post series at /r/IndianCountry that I mentioned elsewhere in this thread that will help illuminate this topic.
Always check the FAQ before asking a question these have all been asked several times.
Also just as a side note the idea of one culture as being more advanced than another is an inherently flawed view. It implies that there is a distinctive direction that humanity is going down that is "better" then the rest. In reality there is no way of knowing this, no culture is "better" or "more advanced" than another, and every culture develops differently. So while there is nothing wrong with your question just be aware that there is no reason why these cultures "should" have developed the way you describe.