Four in ten Britons say animal lives are worth the same as human lives

I think you guys are misunderstanding what Brits mean by that... They value both very little.

Kind of a weird question IMO. I don't even think animal lives are worth the same as animal lives. Is a single deer's life the same as a single ant's life?

I consider myself to be kind and thoughtful towards people and animals -- I'll save snails or worms that I find while gardening, but I also will kill mosquitos that are inside my house, and move spiders outside where they will potentially die.

This isn't even getting into "special" animals like pets

... but I also will kill mosquitos that are inside my house, and move spiders outside where they will potentially die.

huh, i just let the spiders be and they take out mosquitos and other bugs for me. we're symbiotico, that way.
- I'm scared of / uncomfortable with spiders, so they're not allowed inside
- Don't particularly love spiders, but I'll never kill one, even in my house.

I would also answer "Human lives are worth the same as animal lives", simply because Humans are animals.

Never trust the answers to questionnaires with such basic mistakes.

Yeah, I'd like to see the results from the question : I have a gun pointed at your long time childhood friend and one pointed at this cow, now is this cow's life worth the same as your friends life?
- I have a gun pointed at your dog and another pointed at a guy that's going around eating people's pets...
  
  You are mixing the rational component of the question in general with the emotional attachments of particular situations. This kind of "I know it in my heart" drive is the same that drives things like racism and xenophobia.
- A better comparison would be if the human in question was a random dude you pulled off the streets. If this was a cow that I grew up with and shared a bond with, then yeah, I'd obviously pick the cow over some dude I don't know. If it's a childhood friend versus a random cow I don't know? Same thing but in reverse.
- What if your childhood friend is the cow and the other entity at gunpoint is an unfamiliar human?
You know what it means, though.

delusion at it's finest, humans are supposedly the smartest beings on this planet and yet this proportion of them are wasting their heads worrying about their former burgers' life, if the animals were meant to be worth as much as us, they would have developed metalworking by now

Then why do they kill and eat them

Because humans are comically inconsistent and morally bankrupt. The history of our species is basically slavery, factory farms, and HOA’s.

The search term you're after is NRS social grade. It's a UK demographics thing.

Interesting (or, perhaps, expected) that the more progressive/left leaning demographics correlate with a higher proportion valuing human and animal life equally. Sort of makes sense and I'm glad to see it.