"Where research falls down is its applicability in individual cases"
Qualitative research DOES take individual cases into account.
Quantitative research looks at large groups of children and controls for social factors.
Both types of research are needed and both are done.
"a good nanny on nursery is better than a bad parent at home"
Yes - you'll find that this is one of the things that has been flagged up in the most important research, that some children are better off in nurseries because of inadequate parenting.
"Common sense says that we evolved in a hunter gatherer setting for millions of years where children were raised by the 'tribe' and women looked after other womens children all the time"
Ummmm, the research on the few indiginous people who still live this way actually shows something different. Very small babies and children in these societies spend almost all of their time being carried by their mothers and breastfeed very frequently throughout the first few years of life. Yes - women would suckle other women's children on occasion, but the vast majority of women bf their own babies from birth until around the age of 4 or 5. Obviously this necessitates spending a fair amount of time in each other's company!
"Other parents make an educated choice with all the risk factors in mind and they should be respected for it."
I haven't in any way disrespected other people's choices on this thread or argued that people should do one thing or another. I have only talked about what underpins the wider objections against this type of group care for very small children and explained my concerns about it, which I think is fair enough.
I feel that very tiny children learn about the world through their very physically and emotionally intense relationships with those people who they love who care for them on a day to day basis.
Disregarding the research for a moment and talking about something a bit more prosaic, I do wonder how a teenager who is caring for two babies other than mine and who doesn't really love my child (no matter how intensely they feel they care about him or her) can meet my child's needs for truly emotionally and physically responsive care in the way that I could? I am not the best mum in the world but I have always mothered my babies in a very instinctive, physical way - bf them for the first couple of years, giving them lots and lots of cuddles and kisses throughout the day, holding them a lot. What's more pleasurable that being with the person who loves you, and whom you love, most in all the world? Being held and kissed and adored? My babies used to make me laugh all day - they delighted me and I showed that delight and approval back to them. Over and over again they had their worth as emerging personalities validated in the most satisfying, pleasureable way. I really, truly cannot see how they could have experienced a fraction of the pleasure they had being cared for by me as babies had they spent most of their waking hours in nursery at this crucial, brief time in their lives. I think life is tough for most people and it gets tougher as you get older. The baby years should be as blissful and as pleasurable as we can make them. I think if babies could talk very, very few would opt to spend most of their waking hours away from their mothers as tiny babies, no matter how nice a nursery was offered as an alternative.