Few questions about hominin evolution:
1. I understand the two theories now, thankfully... But for the Out-of-Africa theory, it says that modern humans evolved INSIDE Africa, and then dispersed around the world in waves. So, that means that transitional fossils of modern humans must ONLY be found inside africa, right?
But a statement in my book said that Homo erectus migrated from Africa into Europe.. Does this mean that Homo erectus is not an ancestor of modern humans?
When it says transitional fossils, it means that the direct ancestors of humans, right? Like the very hominin species that modern humans evolved from were only in Africa?
Hello! (Ok first up, forgive gaps in my knowledge of this, I'm still trying to make the links between information as well!
)
Firstly, to define
transitional fossil: "any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group."
The key word is transitional, which indicates an 'in-between' of two relative species: it's the fossils of an intermediary form.
For example, lets say that it has been deduced that birds evolved from reptiles - and this could probably have been supported by the findings of transitional fossils, that display
both reptile-like characteristics (the traits of the ancestral form/species) and bird-like characteristics (the derived/'new' traits).
With that defined, as you already know the 'Out-of-Africa' theory (Replacement theory) and Multi-regional theory, BOTH theories agree that "Homo erectus originated in Africa and expanded to Eurasia about one million years ago", but the difference is in explaining the origin of HOMO SAPIENS (modern humans).
Because the Out-of-Africa theory states that Homo erectus (initial homo species) left Africa 3 times and occupied various geographic locations that developed into isolated
populations of different, unique species (such as maybe H. neanderthalensis).
But only the Homo erectus population that remained in Africa evolved eventually into Homo sapiens (as in all Homo sapiens only originated from Africa) and moved out as Homo sapiens to
replace all the other
populations that eventually became extinct.
Hence, just because Homo erectus migrated to Europe, does not mean it cannot be an ancestor of Homo sapiens according to this theory, because remember that not ALL the Homo erectus from Africa migrated to Europe - the Replacement theory states that some Homo erectus populations did migrate to Europe and may have evolved independently into unique species,
but the essential point is that they are all extinct now because those populations have been replaced by the Homo sapiens (the species of the modern human population today) that evolved from the Homo erectus (/initial Homo species) that remained in Africa.Although ideally for this theory to be supported, transitional fossils (fossils of intermediary forms between initial Homo and Homo sapiens) should
only be found in Africa - but this is not true (there have been transitional fossils found other places in the world) - but it is explained away by the multiple aforementioned waves of migrations out of Africa.
Whether or not Homo erectus is the "direct" ancestor of Homo sapiens, I'm not sure - from my limited understanding of what's theorized, it's roughly that Homo ergaster/erectus gave rise to Homo heidelbergensis (Homo erectus still co-existed) which gave rise to Homo neanderthalensis and Homo sapiens (modern humans) - H. sapiens and H. neanderthalensis co-existed until Homo sapiens out competed the H. neanderthalensis populations.
Hope this helps!
Feel free to clarify anything, I know some parts could be explained more in depth.
EDIT: HOW IS EVERYONE FEELING ABOUT THE EXAM?
I also feel like it should be kept in the back of one's mind (as my teacher often reminded us) that a large portion of this section of the course (hominin evolution) are mostly just
theories, and nothing is really solid 100% certain (unlike Unit 3 which is more facts/experiment-based) - so you just need to know how to JUSTIFY (cue Business Management spaz). These things are constantly changing as more things/fossils mostly are being discovered, because as humans we don't really even know what we don't know.
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