Bit of both probably. Doesn’t matter. Scientists have moved on from Orthogenesis. Unfortunately, it sticks around as a common misconception, sometimes museums and textbooks haven’t updated their depictions either.
The right image shows that horse evolution wasn’t a linear progression towards one particular form. Horses of various sizes, number of toes, and feeding modes were living simultaneously at various times. One-toed evolved 2 times among horses (and it also evolved in other groups too) and some horses became smaller.
In other words… an expanding bush ≠ a single arrow
Here is a paragraph from this review paper that is particularly relevant:
Despite subsequent recognition that equid evolution was in fact more like a bush than a straight line (Simpson 1951; MacFadden 1994), it is still portrayed in a linear fashion in many museums and textbooks (MacFadden et al. 2012). Some trends in equid evolution do appear to exist by gestalt—today’s horses are indeed much larger, hypsodont, and have reduced digits relative to the earliest horses. Monodactyly had two separate evolutions, one in the Dinohippus/Equus lineage and one in the Pliohippus/Astrohippus lineage, strongly suggesting at least some adaptive utility and selection for this condition. It therefore requires careful attention to discuss the evolution of horses without slipping into verbal orthogenesis by drawing a straight line between the earliest horse and the lone surviving genus today, particularly given that trends of digit reduction and increasing hypsodonty do exist in at least some parts of the horse tree (Janis 2007). But evidence from diet, habitat, tooth morphology, and digit state do not match the orthogenetic pattern: decreasing body size was common in lineages such as Archaeohippus or Nannippus; not all tridactyl horses browsed; and not all hypsodont, monodactyl horses grazed (MacFadden 1994; MacFadden et al. 2012).
Why are you expecting that later small species had fewer toes? Some did, but what’s your point?
??? Why are you expecting some horses evolved to get more toes ???
I did link it.
They highlighted as clear outliers, which is the point I am making. Evolution isn’t never linear, and apparent trends can even flip.
Right… ergo, human brain size wasn’t linear.
From my impression, there is little consensus on this. Some have said this might be due to a switch to an agricultural diet (which is actually nutrient poorer compared to that of hunter gatherers). Another explanation I have seen is compatible with yours, that humans came to rely on social intelligence, so huge brains were not needed.
It’s also important to point out the fact that big brains isn’t exactly 1:1 correlated with intelligence. Neanderthals had bigger brains than us, but they had smaller frontal lobes but bigger hind brains. This goes to show that human encephalization isn’t really one parameter.
The reason why is that brain sizes increased significantly long before there was any sign of language. In fact, the appearance of language (strongest paleontology indicators of this are abstract art work) seems to coincide more with the recent brain size reduction.
The hobbits of flores are probably descended from Homo Erectus, less likely an Australopithecus species, neither of which show signs of having had language.
I highly doubt hobbits fled to the island to run away from big brained hominins. Especially considering that hobbits themselves were likely descendants of the big brained Erectus.