A bunch of alternate history ideas. Take them. Please take them. 

What if Lincoln shot first?

alt history idea: people thought land animals were smelly and gross so they almost exclusively domesticated sea creatures instead

Alternative history ideas: -What if the Axis powers lost ww2 ? -What if the confederates lost the civil war? EDIT: it has come to my attention that I have commented this from the wrong timeline, ignore this please.

Any sentence that starts with "don't tell the IRA this" is gonna be fun

I think the reason most alternative history stories are about ww2/civil war is because that's some of the few historical events that Americans are broadly aware of. Say "bronze age collapse" and most will be like "bronze age what?"

What if Marc Anthony and Cleopatra defeated Octavian, turning Rome into a whole different beast

No cap, "Alexander the Great lives longer" is literally a story I was already writing before watching this video.

I think the biggest issue with Alt Histories' popularity is that it is often reliant on the reader's own knowledge of history. I consider myself a history buff and am regularly stumped by alternate history scenarios that I know too little about and it really slows down the enjoyment for me (either I'm constantly looking things up on Wikipedia or it can just go over your head completely) The means that writers can gravitate to the more well-known topics (everyone ww2 and all Americans know about the civil war). Even ww1 is well out of the public knowledge. For sci-fi or fantasy, stories can be based upon nothing and that's ok the reader is expected to learn gradually with the characters but AltHis' is different the changes in the world are a far bigger part of the story (as opposed to the characters). Personally, I think a way to fix this is through alternate history set in the modern-day (or recent past) so the changes are noticeable to people. Or to make large changes that don't take hours of deciphering to understand.

I think the giant hand that crushes one person a day is also a good alternative history idea

Welcome to Alternate History Hub: Live Action

I have a few pop culture ones. 1: Elvis doesn't get conscripted and Bob Dylan avoids his motorcycle accident. Causing the British invasion to never happen. 2: The Baltimore Colts lose the greatest game ever played to the Giants. Baseball remains North America's leading sport and the NFL never takes off. 3: Star Wars is never saved in the editing room. The history of cinema is affected by the delay of blockbusters and genre filmmaking by a decade. 4: The satanic panic in the 1980s goes further and allows the government greater power in censoring media in the U.S. 5: D.C gets purchased by Disney and Marvel gets bought by Warner Brothers. Swapping the ownership of the two leading comic book universes. 6: The original vision of Evangelion is created thanks to better funding. Changes anime forever do to being so good. 7: J-Pop rises instead of K-Pop. Possibility due to Gangnam style never going viral. 8: The 2016 Olympic games are awarded to Chicago and the 2020 games are awarded to Rio De Janeiro's. Because of the COVID-19 pandemic the 2020 games are cancelled. Also the 2024 Olympic games take place in Tokyo instead of Paris with 2028 is when Paris holds their games.

Some other ideas: Marc Anthony and Cleopatra win against Augustus. Christianity doesn't become mainstream in Roman empire (if it exists at all). Yellow Turban Rebellion doesn't happen or is supressed more effectively. Arabs fail to conquer Sasanian empire. Norsemen continue colonisation of North America. William the Bastard fails to conquer England. Ottomans manage to conquer Vienna. Japan wins Imjin war. Bohemian revolt is successful. Gran Colombia manages to survive. Francoists get defeated during Spanish Civil war. Israel isn't founded.

What if events during the Great Depression and post war period in the US led to socialist political parties coming into the mainstream and breaking the two party system, the most influential New Party being almost completely ideologically opposed to the USSR and PRC?

21:50 - That's a really common misconception, but the Madagascar plan was actually _not_ "how about we ship all the Jews to Madagascar and let them have their own little country over there". The plan was to put them there under a police state directly governed by the SS, in a region of the world that couldn't even have supported several million additional people (on top of the four million who already lived there). The Madagascar plan essentially amounted to picking a different location for the same genocide, and the Nazis never saw or internally framed it as anything but that either. They only settled for Eastern Europe because of the British naval blockade. So there would have still been a holocaust, just in a different location.

Cogito has a good video about how Australian aboriginals had very effective methods of making their environment more fertile and optimising the plants for their benefit... before Europeans destroyed almost all of it again and tried to impose their inefficient agrarian systems.

*Silently takes notes*

I will like to recommend you the korean Drama "The king eternal monarch" is about what if korea had won over the japanese invasion and stayed as the kingdom of Goryo or Joseon.? Is about the collision of this dimension with an alternate version when that is what happened.

I've only looked at the thumbnail but there's no need to say anymore because I've got the idea. You're suggesting a sonic the hedgehog alternate history crossover right? Genius! I'll begin publishing George Washington X Amy rose and Nicola tesla X Tails fan fiction immediately! How could. No one have ever thought of this! Thanks for the one million dollar tip friend.

What if Tunguska Asteroid (30 June 1908) strikes one of world major powers' capital instead of Siberian Wilderness? For scale, its explosion is estimated to have power of around 15 megatons in TNT equivalent, about 1/4 of Tsar-Bomba.

I think the most mainstream example to me would be Watchmen, where it actually examines what would happen in superheroes really had existed since the 1940s, from mundane stuff, like altering famous images or one of the heroes being the assassin who killed JFK, to President Nixon getting five terms because the guy who killed JFK also withheld evidence at the Watergate trials... Wow, The Comedian was an ass... Anyway, just watch the opening credits of Watchmen. Also Inglorious Basterds.

If we wait a few years someone could write a version of history where COVID-19 never hit.

When you made that video about the Australian alternate history book, I was like "please make a video about your better alternate history ideas! This genre is so stagnated." You did not disappoint me. Your chinese nation states idea is my favourite. Followed by the unified Ireland and HRE.

Here’s a fun one: what if the Council of Nicea had produced a Syncretic version of Christianity, instead of the one we have? I could see Christianity being simultaneously more prolific and less agressive.

I like Kaiserreich (what if Germany won ww1), it takes a simple premise but it's really interesting, basically every country is different from it's historical counterpart. There is also some great media for it that Kaiser Cat Cinema has made.

The thumbnail scares me.

So there is a lack of Africa alternative history here so here are a few: What if mansa musa’s expedition to the American was successful? What if Shaka Zulu was not assassinated and successfully United the south of Africa? What if after colonialism ended in Africa, Africans made more capitalist (rather that socialist government)? What if the Nubians conquest of Egypt remained? What if Madagascar was unified, had more resources, and participated in the Indian Ocean trade more extensively? what if an African costal empire existed? Lastly, What if Africa’s economy was not dependent on the slave trade?

I’m not much of a writer but as a linguist your mention of the Mongols gives me an idea: a Mongolic language spoken long-term somewhere around eastern Europe with heavy East Slavic and possibly Ugric influence

There was a very brief moment where someone sent an offer to Prince Henry of Prussia- a Hohenzollern- to make him King of the United States. He refused, but ... you know, weird timeline

There actually is a good candidate for the Pacific continent you mentioned, it's called Manihiki and though most of it is underwater it could've maybe been above water in some alternate history. It's only about 10% of Australia in size though.

For the "Madagascar Plan" Attack on Titan is probably the closest thing we have to a show exploring that but obviously with a lot of fantastical elements

You should check out the TV show For All Mankind - it's an alternate history where the Soviets land on the Moon first and the Space Race continues.

Speaking of alternate history, Have you ever heard of The Draka Dominion series? It might be something worth covering primarily because of it's infamy among alt history communities for feeling more like a fantasy story than any possible scenario that could happen in history...that and The Draka themselves are possibly one of the most vile dictoriships in any media. (Seriously in the first book they legit make the Frickin Nazis more rootable.)

13:29 what if High King Brian Boru, his son and his grandson survive the Battle of Clontarf in 1014

I too remember Shadow the Hedgehog being there for the Gauls surrender to Caesar in 49 BC.

There is a similar book to your idea about separate Chinese states. It’s called The Disunited States of America, it uses the U.S instead of China. It has a weird plot point of parallel time lines but does dive into some of the differences in culture, like how slavery still exists in some states.

These are some really great ideas...I do hope some aspiring authors will take this genre into exciting new directions! One issue I have with some alternate history media, particularly the most famous one "the man in the high castle" is this sense in writing that this is the "wrong timeline" like yes if the Axis have won it would likely be worse than it is now but it doesn't have to be a full dystopia, like maybe the nazis win the war but are overthrown in few years and new powers take place ...this idea that the timeline needs "fixing" is just not interesting for any history fan, I want to see an exploration of different timelines not an affirmation that our timeline is the superior one!

Dont know if I'll start a book or anything but I'm definitely going to be doing more history research this is pretty interesting

I want an alternate history where anarchists exists and their ideology is not just treated like "me want chaos" or "I am an idealist but also stupid".

Al-Andalus became majority muslim during the 10th century people reconverted to christianity as the reconquista gained steam

alternate history hub has a lot of short but realistic ideas for alternate history scenarios

There's thisnone I worked on for a while but didn't take very far. What if, during the 60s and 70s, instead of computers becoming the cool new thing and biotech something evil and scary, it was the other way around.

What if John McCain was born in 16th century Poland?

what if the cavaliers had won the English civil War and charles i had never been executed? VERY wide ranging implications there.

What if poncho villa won the Mexican revolution?

What if the English commonwealth out live Oliver Cromwell?

The History of the Siege of Lisbon is not only an alternate history story, but a story about a man writing about alternate history. I thought of it when you talked about the Iberean Peninsula. It's kind of "what if the crusaders DIDN'T help the Portuguese king take Lisbon back from the Moors". Saramago is a Nobel Award winner. He's very good.

A few I've been thinking of What if the US allowed Hawaii to remain a monarchy, could the state have been a constitutional monarchy today? What if the Suez Canal existed when the Ottomans ruled Egypt, would the Ottomans have gone colonial like so many other Europeans did? Also one I am genuinely invested in What if Russia instead of selling Alaska to the US, protected it by entering a mutual defense pact with them This would have been a just as effective way of protecting Alaska from Britain as selling it to the US, and if they had done it just a few years earlier they would have gotten the perfect opportunity to solidify the pact by aiding the Unionists during the American Civil War

me walking into the "what if germany won ww2?" alternate history convention and sharing my alternate history where they lost even harder

Also, here are some alternate history scenarios I've been working on: -The activities of 1930s - 40s Germany, but the Third Reich never came to power/the Weimar Republic stayed in power -What if Justinian had succeeded in reacquiring and reincorporating the former territories of the Western Roman Empire? -What if the Western Roman Empire consolidated power in Britain or its influence remained dominant/Romanized Brits were successful in keeping their pocket of the empire alive? -What if the Hussite Wars ended in an overall Hussite victory? -What if the Norse/Vikings who settled in America had established a strong relationship with the natives? -What if the Eastern Roman Empire fell and the Western Empire was the one that stayed intact into the Middle Ages? -What if Ramba Ral got his Doms? -What if Ptolemy I beat his competitors and reunited Alexander's fragmented empire?

well going really far into the past like a landmass in the ocean would really change everything, even the course of evolution is some ways

I’m guessing this one’s been used a few times, possibly also by alternate history hub, but here goes: what if Archduke Franz Ferdinand isn’t assassinated? Would World War I even begin, or would it begin later and be worse? How exactly would this change things?

I've seen a few alt history videos I find very interesting: 1: Vikings stay in America. The vikings brings their knowledge of iron working and travel south and meet the native americans and intermix with them. Some Viking travel far enough to meet the Mayans. 2: Ancient Greek invent steam engine. The Persians hires the Greeks to build them a rainroad network while the celt build steam ships and colonize america, aslo eveyone worship the sun.

Probably my favorite video from your channel. Awesome stuff.

What if the American populist party of the 1890's became a major party?

the TimeRiders series had a few similar ones : the Civil War turning into an endless conflict replacing both world wars and the Cold War, saving JFK, Richard Lionheart failing to reclaim his throne after the crusade, leading to England's collapse

One of my favorite alternate history series is the Front Lines trilogy by Michael Grant. The basic premise is “what if women were allowed to serve on the front lines of WW2?” which admittedly is not a very original premise but it does it really really well

My two favorite scenarios are: 'What if Spain won at Manilla bay ?' and 'What if Melios managed to convince the Athenians ?'. Then there is also: 'what if the cotton gin was never invented'

The thing with Dalajlama is actually pretty easy... It's just the Avatar from the Avatar. Eternal cycle of rebirth, there's a special set of rituals and methods to determine who is the next one.

Liked the video, that's a lot of detailed and original ideas - I agree that for most of them, the ripple effect would be extremely far-reaching, so it would probably be pretty difficult to imagine the new timeline over a century after the divergence point?

I got one. What would the cold war be like if there was an extra front to consider... Japan. If the Russians got there before the nukes could be dropped, so Japan essentially gets bisected in two, Korea style.

One I'd love to see done is the Yellowstone Supervolcano erupting sometime during our past, and seeing how it changes the course of history. It effects the world almost as much globaly as it would effect the American continents. Global temperatures dropping by 10 degrees would have profound effects, as would the first Europeans setting foot on American soil not long after an eruption. Having it happen anytime after the colonisation of the US would be interesting too, hearing about the first colonies struggle and maybe collapse after a cataclysmic event would be cool, maybe having Native peoples take advantage of the situation and the technology left behind by these failing colonies to rise as a new superpower. It would be interesting all the way up to modern day, seeing the world change with a crippled USA and a global cooling.

The rule for most alternate histories is that the farther they get from the POD the more outlandish they get

To go along with your continent in the Pacific idea there could also be scenarios involving Zealandia not sinking (a bigger New Zealand), the Izu-Bonin Mariana Arc rising to the surface (a bigger Japan), etc. With the Green Australia idea, another one could be a green Sahara which could in turn let the Egyptians (or some other power/people) expand beyond the Nile.

I'd like to think of that "What if there were a continent in the Pacific" scenario as the "Skull Island" scenario.

What would happen if the Skywall Disaster in Kamen Rider Build happened in America?

"What if Austria-Hungary..." *Black Rose Rebellion intensifies*

An idea I had once was, What If Aliens invaded during WW1. How would humanity fight them and each other?

Another good idea is "What if Oda Nobunaga was never assassinated or survive the assassination at Hongan-Ji" He was a massive Xenophile with a love for western culture, he has an Ethiopian retainer by the name of Yasuke, he also has ambitions to take China and beyond.

Shadows of Doubt, while not being focused on alternate history, does a great job with an imaginative premise.

I had a D&D campaign I ran where the introduction of magic halted the Invasion of Gaul and led to a bloody stalemate between the Roman, Germanic, and Celtic spheres of influence. It was a fun idea to mess with, and anyone else is free to use it if you guys are interested

I'm glad you mentioned the Mongols. If they didn't turn around in middle of the Europe's conquest, there is a pretty significant chance that they would have conquered a large part of Europe, if not whole continent. And even if they were stopped, the political structure of Europe surely would be changed significantly, which definitely could make for interesting alt history story. So to add a suggestion on top of what you already said, what if Subutai didn't turn around after the Khan's death and continued with the conquest of Europe?

Also I remember alternate history hub did a video on what if america became a monarchy but that might have been a fever dream of mine or something

I think for India it would be if baji Rao peshwa of Maratha confederacy didn't died of heat stroke that guy way military and administrative genius he fought in 41-42 battles and didn't lost once he is also reason mughal empire territory was reduced to city state In just 20 years he saved other armies by traveling ridiculous distance and defeat army 3-4 times it's size he also successfully defeated Portuguese armies in naval combat one of greatest general of his time only to die of overwok and heatstroke other Maratha generals took over 75% on India after his death only to squabble later without a proper administrator (peshwa means prime minister) and opening door for colonization Edit : also similarly to Japan chatarpati of Marathas (basically emperor or king) became figure head of various Maratha and Deccan families.

Thank you for all the videos man. a couple questions, do you write? how do you find the time/motivation?

I usually hate alternate histories, because usually the writer knows nothing about history in general. So there's one interesting idea, but no interesting development, and it falls into fan fic-y cliches.

My Alternate History Ideas: - What if Vikings created a long lasting empire conquering most of Europe, creating alliances with Asia through trade and colonizing the Americas with places like Vinland and Greenland - What if George Washington became the first King of America (Don't really care how as long as someone makes it make sense) - What if almost the entire population of Europe was wiped out by the Bubonic Plague, leading outside nations like Africans, Arabs, Turkish and Mongols to start colonizing the continent and having caucasians become a minority. Christianity is basically wiped out leading Islam to become the biggest religion - What if the Bubonic Plague never happened to begin with - What if The Great Depression never happened - What if The US never developed the nukes to defeat Japan. Would the war last longer? More or less casualties? How would this affect the Cold War? - What if the Soviet Union won every conflict during the Cold War and survived to modern days?

Here are some more ideas: Admittedly some of these might a bit beyond 'just' alternate history, but I think they're all interesting concepts. -What if no country ever abolished their absolute monarchies -What if the Pope ruled all of Italy -What if the position of the Pope was monarchical -What if the world only had one religion -What if all world religions were treated as mythologies, like how we treat the Greek and Norse gods etc. -What if the world had no religion -What if Germany won WW1 -What if WW2 was still being fought today -What if human language evolved to all universal so language barriers didn't exist -What if the British Empire conquered the whole world and were still in power over all of it -What if humanity never had an industrial revolution -What if the industrial revolution happened in the middle ages -What if the dark ages never occurred -What if the enlightenment period never occurred -What if the aeroplane was never invented -What if the black death never occurred -What if humans never migrated from Africa -What if humans all had the same colour skin -What if no country had ever abolished slavery -What if humans hunted all animal species to extinction -What if cannibalism was commonplace -What if the Earth had never experienced an ice age -What if the Earth began entering an ice age within the last 2000 years -What if sea levels were 10 metres higher -What if sea levels were 10 metres lower -What if the Earth has no seas, only large lakes -What if the altitude relative to sea level of every place on Earth was the inverse of what it is -What if the Earth was either tidally locked, or didn't rotate at all -What if the Earth didn't have a moon -What if Pangea never broke apart -What if Pangea recently reformed -What if Neanderthals never went extinct and modern day Neanderthals couldn't breed with modern-day humans -What if Dinosaurs never went extinct and were still top of the food chain -What if humans weren't the only animals to develop opposable thumbs and a high level of intelligence: e.g. dolphins -What if human biology had only one sex -What if human biology had more than two sexes

I’ll make a video on one. Thanks for the ideas dude

Agreed, alternate history is underrated tbh to use in Fiction

It's videos like this that makes me love this channel ❤️😍👍

A new idea for alternate history could be if the Spanish Armada succeeded in invading and taking over Tudor England. You also have the outcomes of Battle of Hastings and Battle of Stamford Bridge. What if it hadn't been windy and bad for sailing and the Normans arrived first? Would they be defeated, then Harold and the English would have to head over to the Vikings and, weakened, lose? Usually it's the other way around, but basically what if another people ruled England. Except the second is earlier, maybe changes are more extreme, or less? How would Catholic rule effect a growing protestant Tudor England? Would it be more burnings? How would they deal with the religious conflict? I am saying this because I'm learning it in school, but Idk. Could be alright-maybe..?

Regarding Anatolia and what if the Romans won the battle of Manzikert: More interesting than what the Seljuks would do, would be that without the loss of Anatolia, Alexios probably wouldn't see the need to ask the Catholic pope for help and the crusades wouldn't happen. It would be interesting how Europe would behave without the technological and cultural exchange that happened due to the crusades.

I would also love to read a book of what if Islam was a bigger, or even default, religion in Europe, having the Moors convert the Iberian peninsula would be a great starting point. It would also be interesting to know if the relationship between Christianity, Judaism and Islam become different through time. More ideas: - WW1 never happened, the inciting event never happened, WW2 was therefore unable to happen. How does the world progress? - Industrial society didn't become lucrative in the British Isles, but elsewhere. Perhaps India, Iraq, Mexico or Japan, for example. This would drastically affect the outcomes of wars, politics and colonialism, but in what ways exactly? - What if successful slave revolts were the norm in early American colonialism? (basically Haiti wasn't an exception but a rule) - What if the American Civil war ended in a stalemate or never ended, and as a result two "USAs" were born? - What if African kingdoms managed to become more influential and wiped out or colonialized Europe? - What if Japan was somehow connected to China or Korea by a land bridge? (maybe the Mongols could actually have conquered them and THAT would make interesting alt-history) I'm not a history expert but an anthropology student, and knowing a few things about world archeology generally there would be a lot of logistical and resource questions that I think would be fascinating in these scenarios.

Many thanks

Interesting ideas. For making an original Althistory one only needs to do is to find an obscure event that could have turned into something. The thing I'm working on is what if the Northwestern Boarder Crisis of 1859 (the Pig War) actually turned into an early World War 1.

Lion's Blood by Steven Barnes is the only unique one I can think of that I loved. It's about America being colonized by Africans instead of Europeans and battle the Aztec empire

I've got an idea or two that are mostly unironic. Mostly. What if Japan won the Imjin war, or later, what if Shogunate forces won the Boshin war? Both of these functionally have the potential to massively change the balance of power in Asia or the character of the Japanese Empire as a whole. What if Russia won the Crimean War? I imagine this setting would require a bit of mary sue imperialism around Russia to justify them doing cool things like winning the war and going on to take over Constantinople or something without getting immediately beaten to a pulp by coalition of enemy nations, but it could be interesting nonetheless. What if China modernized? The point of divergence for this one could be placed pretty much anytime after 1400 where you imagine a scenario leading to China being more open or more receptive to outside ideas, leading to greater technological and economic growth and less stagnation of ideas, making them more fit to be a world player instead of a regional superpower waiting to topple over at the slightest prodding by an outside colonizer. I imagine China in this timeline as a very strong nation prepared to enforce its will even on far away nations through careful control of trade and leverage of power. Quite unlike our own timeline and contemporary time period. Unironically this isn't so much alt history as it is asking "What if modern china but 1600 and also monarchy" which is the sort of wacky bullshit I go to this genre for. If you want to get really edgy and topical, "What if 'X' religion didn't exist or was functionally snuffed out at 'Y' decisive encounter" is always a goldmine. Just remember, they aren't neopagans if paganism never fell out of fashion. What if the US broke itself up early into its history? This one's pretty silly, but I like the idea of states being hyper disunified long into the modern era, to the point where they have their own standing military and such, going beyond even the typical confederacy government that would be employed for this sort of alt hist scenario. What if the US lost the battle of Midway? This one's one of the more defined and serious scenarios. I watched 2019's Midway recently, and in it, a character worries that losing a decisive victory at Midway would lead to the war dragging out for years and years while the west coast of the US gets ravaged by Japanese air raids. It's a great scene and one I feel could support its own alt-historical work.

I'm gonna use at least one of these for a GURPS game, thank you

Dunno if you bring something like this up later in the vid but what about a world where European influence didn't spread as much? Natives fought them off or something when they discovered place. I know it's incredibly vague but i bet you could do something with that

kinda needed that about fantasy too

Late comment but one of my favorite alternate history subjects has been the viking age norse colonization of America. What if Vinland became a country and managed to continue on existing? The Norse were interesting in the way they colonized places that already had sizeable human populations, where they would assimilate into the native culture just as much as they would introduce their own influences. A hybrid society of pre-christian Scandinavians and first nation peoples would be fascinating to look at, especially with the Viking talent for navigating river systems with their longships. What if instead of lewis and clark it was Leif and Cnut?

I feel like the idea of the axis all-out winning ww2 is overdone but there are definately still interesting things you can do with the nazis in alternate history that haven't been done

What if Charleman left his empire unified? Eather just impartable inheritance, or even more extreme a system of slow inheritance like Tokugawa Ieyasu. What if WW1 ended in eather a rather equal peace treaty or the central powers straight up win? (No American entry, less agressive Germany in the west, no english war entry) What if the Assasination of Franz Ferdinand failed?

I wanted to make a D&D campaign setting based on Crusader Kings playthroughs with my friend and try to make realistic reasons for how it happened. It'd be hard to explain why the Seljuks changed their religion to a sect of Kemetism and how the Visigoths took over the byzantine empire when it was in its prime but it'd be fun to make

Going by purely geographic history, we could for example change the elevation of Sundaland and Doggerland to be above modern sea levels. And bang everything from sea currents to nation building changes.

The extra continent idea seems more a spec bio prompt than an alternate history one. The POD would literally be billions of years in the past, and have a large impact on the evolution of all life on the planet. It'd be land that would otherwise be water, changing ocean currents significantly, which would drastically change climates and biomes, thus leading to different pressures on different populations, resulting in a shakeup of the entire tree of life as far back as the Cambrian, if not further. And this is _without_ starting on the actual land part itself, let alone anything to do with plate tectonics. Beyond the broad strokes, _anything_ could happen. Arguably, an Earth with a continent in the Pacific Ocean would be unrecognizable on the ground, things would be that different. It'd be interesting, not quite starting from scratch like a xenobiology project would, but you would have to come up with a lot of things yourself past basic stuff like chordates, arthropods, and molluscs. You could stretch it a little and assume certain adaptations would happen the same way, like gill arches and subsequently jaws, vertebrate-like eyes (which managed to happen twice in OTL, see cephalopods), fluffy integument, reject bilateral symmetry become star (seriously echinoderms, just why). But you could also go wild, give the major land vertebrate clade six limbs, or have molluscs develop complex internal skeletons and take over the world, make the plants red! As long as you don't just rehash existing history, anything is plausible. (The funny part of this particular scenario is that if you decide to throw in a sapient species roughly around when humans would spring up, some countries would have similar borders to ones in OTL. Imagine Italy, but it's inhabited by fuzzy squid with six legs.) If someone wants to take this idea and run with it, be my guest.

Did he just say “relativity small island like Australia” What?????

What if Constantine didn't convert to Christianity? What if Wessex lost and England became norse? About the romans loosing in Alessia, one of the biggest strengths of the romans was that they could loose battles and have other legions to go and fight again, most big conquering movements had one big army and a single lost battle ended their growth or even led to the collapse of the movement.

Than there is the Fantasy/SciFi Alternate History, What if during the Napoleonic Wars we had domesticated dragons that could be used for air forces. I'm still sad that the Temeraire/PeterJackson mini series never ended up getting made. Amazon/Netflix get on with this already!

On the subject of Alesia and the Gallic Wars, I've had a discussion in a group of historians and reenactors. So, let's bring more context to this: First, Alesia was not the final point of the conquest of Gaul, but of a gallic rebellion. Gaul was already roman. Yet, let's say, what if the Gauls had won against the Romans ("Celts" is a very vague term for a bunch of people across Europe, "Gauls/gallic" is more specific to the group concerned, as Gauls had more common elements than other celtic cultures -like, say the Britons in England, the Celtiberes in Spain, the Galates in Turkey...). We speculated that... little to nothing would change, actually. First of all, even before being conquered, the Gauls were heavily influenced by the Romans (and the other way around, as well). The two cultures had been trading and exchanging for quite a long time, and it was very common among gallic elites to have a roman education. Even during the Gallic Wars, many tribes had joined the Romans, and some more stayed neutral. Even stuff like druidic education was already disappearing. And for the tribal society we'd like to imagine... Most tribes were ruled by a senate. Based on the roman republican system. Secondly, we tend to overpower the Romans as well. They were not as much as a monolithic unified empire as we think. In this time, it was more of a vassal-based empire, with provinces doing stuff their own way. Even after being conquered, the gallic tribes would somehow keep their sovereignity. So, roman rule really did not change much on their level. It was even common to have Gauls help the Romans in their wars. In the end, it would be more of a situation akin to the relationship between USA and Canada: sure, they're not one, single country, but they're very close to each other, and often act together in global politics.