Perhaps the finest example of man-beast in popular culture nowadays is the combination of man-beast found in popularly reported cryptids; apeman, goatman, lizardman.
Are we reporting beings that are in the woods but humanizing them in our descriptions? Are we carrying on legends born of imaginations of those embarking into the woodlands and imagining what could lurk behind the bushes or in the caves? Might it be that there are some kind of strange aberrations in nature that create features we attribute to man, i.e. walking upright, and yet physical characteristics of very not-man-like creatures? Has there been some kind of genetic manipulation by an outside influence such as alien creators or some kind of breeding possibility in the past that mixed animals that can no longer breed?
Bigfoot is the Apeman in this scenario and the most witnessed man-beast of them all. In fact, I had seen one almost 30 years ago in the Sierras in California. I didn't expect to see one there. I had the same thoughts most folks did, that they only existed in Washington State. But, what I saw forever changed my view of what Bigfoot was. This was no ape. It was a man. The hair was impressive, but the confident stride, the ease of being upright, the proportions were slightly off, but very much like man with powerful glutes and quads.
Maryland reports a man-beast called the Goatman. This being, however, is a bit different than most man-beasts; he was reported to be axe-wielding which is rather interesting because where I grew up in Fairfax, Virginia, not far away, we had a legend of a Bunnyman who did the same. Now, in the convoluted way these legends go, Kentucky claims something called a Pope Lick Monster that is part man/part goat. With so many legends in such a geographically tight area, each having variations but each using characteristics, either a goat-man or an axe-wielding man-beast, one has to think of these as local legends based on scary locations, off-limits lonely roads to railroad bridges. Even the Bunnyman was associated with a trestle bridge like the Pope Lick Monster.
The Lizardman is perhaps the most amazing of the claims. The concept of mixing a reptile and a human sounds positively impossible, and yet supposed alien abductees do report a reptilian alien species. This supposed cryptid is reported in South Carolina. They report him to be 7 feet tall, with dark body hair and scaly skin on his hands and face. It leaves behind three-toed footprints. They are also reported to have a tail with spikes and an angry disposition, attacking cars. Interestingly, Lizardman has been reported in caves around the world. The stories are quite unusual and involve a whole group of these beings hiding in caves and using some kind of alien technology. If something like this existed, it is so far from being a natural creature, that it would almost certainly have to be alien. It's quite an extraordinary legend, but the descriptions are so exceptional, like the Goatman, that it seems quite unlikely.
Are there true man-beast hybrids like these? I seriously doubt it. Even the one we used to call Apeman or Bigfoot is not truly a half ape/half man. We are very likely to find out in the end that we are dealing with human lineage and the hair is simply an adaptation of living in the wild just like feral people grow thicker and coarser body hair, but over thousands of years this would have developed even further.
As human-like as this hairless ape is, I don't think any of us seeing him in the wild would say "that was a human!" His shape is completely wrong, even though he is hairless like us. But, you take a Bigfoot, who has our shape and walking capabilities and put hair on him and we call him an ape. It makes no logical sense.
So, man-beast? Not truly. Either man or beast. No in between, though some humans certainly act like beasts and many beasts act like humans, such as the family dog.
To me, the Goatman and Lizardman are too extraordinary a concept and don't have enough witnesses and staying power to be feasible. Now, if such a thing could exist it would be in the most unusual of circumstances; either genetic manipulation by an advanced technology or something of a spiritual nature in the form of a shapeshifter. The most likely explanation, however, is that they are legends that fill us with upset and dread at the concept of mixing a human and an animal - the ultimate abomination to most people.
What does exist? Bigfoot. But, in this case, we are talking about family of man, simply a hairy one.
Still, the concept of half man-half beast is a truly intriguing one. Imagine a Lizardman - he might need a hot climate, he might be able to regrow limbs, or he might be able to see at night? One never knows what facets of man and beast he would take on. In fact, it would seem recessive genes and dominant genes would be at play with these creatures mating with their own - eventually a very man-like being would emerge with perhaps dry skin and thermal issues or something very lizard-like that cannot walk. Given the concept of having a breeding population and all the variables of man-beast outcome, it just doesn't fly for me.