In a film full of badass moments that make you pump your fists and grin like an idiot, one of my favorite moments from Avengers: Infinity War comes during the Battle of Wakanda, when Captain America and Black Panther race out in front of everybody to get first crack at the Black Order and the Outriders. The scene showed just how similar in power and bravery these two heroes are. Now a new theory connects Black Panther and Captain America beyond just their similar heroic traits. According to the fan theory, the Super Soldier Serum that made Steve Rogers Captain America actually comes from the Heart-Shaped Herb that gives Black Panther his powers.
The theory comes from Reddit user 4DimensionalToilet (great name) and begins with the premise that Captain America and Black Panther have very similar powers of enhanced strength and speed, as we've seen in their contests together and against one another in the aforementioned Avengers: Infinity War and Captain America: Civil War. We know that Captain America's powers come from the Super Soldier Serum created by Dr. Abraham Erskine. Dr. Erskine was the only person ever to have perfected it the serum, but that was after a failed attempt that turned Johann Schmidt into the Red Skull. It was only when he joined forces with Howard Stark did the formula prove successful with Steve Rogers. We also know that Howard Stark presented Cap's shield to him. The shield is made of vibranium, which is only found in Wakanda, which makes where he got it not difficult to figure out.
Perhaps when acquiring the vibranium for Cap's shield, either himself or via a third party, Howard Stark heard about the Black Panther and his abilities. Stark being Stark, he obviously sought this as a part of his work with the military. At some point, Howard Stark could have brought this information to Dr. Erskine and set out to use the Heart-Shaped Herb to create an American super soldier. Perhaps Stark obtained it through some sort of trade or he stole it outright, but the Heart-Shaped Herb winds up being the key ingredient in the serum, stabilizing it to prevent the kind of mutations that happened to the Red Skull. So the similarity in powers between Black Panther and Captain America is a result of both of their powers being derived from the Heart-Shaped Herb.
This is definitely a fun theory that establishes a bond of origin for the two heroes' powers, but there are some things that seem to go against it being canon. Presumably the reason the serum finally worked was due to the Vita-radiation chamber and not some special ingredient in the serum. It also worked because of who was taking it. The process brought out who Steve Rogers was on the inside, the same as it made Red Skull as ugly on the outside as his internal beliefs.
There is also the matter of the Heart-Shaped Herb. Given how great Wakanda is at secrecy and hiding its true nature, it seems unlikely that they were having dealings with Howard Stark. And there's no way they would ever give him, or any non-Wakandan, the Heart-Shaped Herb. It just doesn't jibe with their isolationist philosophy or the sacred importance placed on the herb. What's more likely is that Howard Stark didn't get the vibranium from Wakanda. The vibranium comes from a meteorite that crashed in Wakanda, but other, smaller pieces could have landed elsewhere and Stark's team simply found a deposit.
Even if it's not canon, these fan theories are always fun as they drive greater investment and a more careful analysis of the MCU films. There will be no shortage of fan theories as we count down the days until Captain Marvel and especially Avengers 4, both of which have a fair bit of mystery surrounding them.